AUdIoCoUrSeS
Joined: 31 Oct 2002
Posts: 2014
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| Week 8 - Mastering |
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1. What is Mastering?
2. Why is mastering necessary?
3. What is Post Production?
4. Comment on “preparing your tapes”.
5. Comment on “stereo bass”.
6. Why is mono compatibility such an issue?
7. What is meant by the term “start ID”?
8. What are the three types of Disc Cutting?
9. What information should be written on your master tapes?
10. What is meant by multi-band compression?
11. Explain the term dynamic range.
12. What is the formula for dynamic range?
13. What is meant by SNR?
14. Describe gain riding.
15. Comment on this article:
http://www.digido.com/index/pmodule_id=11/pmdmode=fullscreen/pageadder_page_id=93/
Pay particular attention to what you feel about the subject. Essentially it is about where YOU stand on the subject within the big picture. For example are you joining the race or are you sitting on the fence? What would you do given the reins to a potential top ten album?
16. What is meant by normalling?
17. Explain DC offset
18. How can the target audience affect mastering decisions?
19. What happens to the audio signal when a aural enhancer is applied?
20. What does relative loudness mean?
21. What does r.m.s. mean?
22. What is meant by 'entertainment quality'?
23. What happens if you leave excessive, short transients in the music?
24. What is The K-System?
25. What are The Equal Loudness Contours?
26. What is MetaData?
27. Explain the term Headroom.
28. Explain the term Crest factor.
29. What skills and abilities must a Mastering Engineer possess?
30. What does the term “Masking” mean?
31. Explain the Hass Effect.
32. Why is an acceleration limiter necessary in a vinyl cutting lathe?
33. Explain, as separate paragraphs of up to 100 words, the two causes of mistracking of a vinyl record.
34. Why is the bass on a vinyl record mixed into mono?
35. For maximum sound quality, what is the suggested duration of a single side of a vinyl record?
36. What is a 'production master'?
37. On a CD, what should the peak level be, at some point in the recording, in dBFS?
38. What is the maximum recommended duration of a CD?
39. Why is it possible for two recordings to differ in subjective loudness even if they peak at the same level?
40. List three methods of increasing subjective loudness.
41. Briefly explain the function of a multi-band compressor
_________________
It's all in the ears. - Learn the concepts not the software.
Audio Courses is a way into the music business for you
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Mon Oct 25, 2004 10:57 am |
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Rico1210
Joined: 03 Aug 2004
Posts: 39
Location: Newcastle, UK |
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Hi,
here are my answers to this weeks questions on Mastering.
Found them quite tough this week, especially as we had about 55 questions on MIDI from Ben 
1. What is Mastering?
Mastering is the final stage of music production. It is where the sound is evaluated on a high resolution monitoring system to address any deficiencies. The sound is processed to make it sound louder, more natural, warmer, clearer or whatever is required, also the mastering process removes unwanted noises or glitches. If an album was being mastered, the mastering process would include the layout of the tracks and any gaps or fade ins/outs would be entered. The outcome is a master that all copies will be made from.
2. Why is mastering necessary?
Mastering is necessary to improve the sound quality of a project and to bring it up to professional standard. This includes making the mix more compatible with a variety of playback systems. To quote a website 'mastering is the difference between ending up with something that sounds good and something that sounds professional'
3. What is Post Production?
Post Production is what takes place after the basics of a project have been put together, when you are happy with the elements of the recording or song. It includes adding effects including compression, limiting and noise reduction. Mastering takes place in post production.
4. Comment on “preparing your tapes”.
"Preparing your tapes" relates to the preparation of recordings for mastering. Whether they are analog tapes or digital tapes, they must have the correct information on the labels. This includes album title, artist, date, contact phone number and tape number if applicable, as well as technical information ie. sample rate(eg 48kHz), wordlength(eg 16bit). Different mastering engineers will have their own requirements for how tapes should be prepared for mastering, the following are a few of the requirements of 'Digital Domain'. Analog tapes: Begin and end the reel with some "bumper", followed by leader. If possible, put leader between songs. Tape should be slow wound, tails out. Label each reel with the album title, song titles, running times of each cut. Indicate tape speed, record level for 0 VU in nw/M, record EQ (NAB or IEC), track configuration, and whether it is mono or stereo. DAT (Digital Audio Tape): 44.1kHz or 48kHz sampling rate, preferably 48 kHz, since most lower-cost A/D converters sound better at 48K. Include a cue sheet or label the DAT J Card with album title, song titles, start time of each cut (in abs time), or length of each cut if DAT cue times are not available. Always make and keep a digital backup (clone) before sending a DAT for mastering. If possible, record tone at the head, a calibration tone of 1kHz at a digital reference level corresponding with console 0 VU
5. Comment on “stereo bass”.
In reference to vinyl recording, stereo low frequencies cause the stylus to move up and down and may lose contact with the record. This will make the groove disappear and cause mistracking. This is why bass is mixed into mono on vinyl.
This answer is the same as my answer to number 34, I would appreciate a little direction on this question as i'm not sure what is required.
6. Why is mono compatibility such an issue?
Mono compatibility is a big issue as not all systems that the project will be played on will be stereo. On a mono system the stereo tracks are mixed down into one mono track, this may give the project a completely different sound. A project should be mastered to be compatible with lots of different systems, and still sound the same.
7. What is meant by the term “start ID”?
A 'start ID' is a marker on a tape that signifies the start of a song, so it can be easily found by an engineer. All songs should have a marked start ID to enable the mastering engineer to skip directly to them. On a Digital Analogue Tape, the start ID can be automatically found by the tape deck.
8. What are the three types of Disc Cutting?
The three types of disc cutting are onto an acetate, lacquer and direct to metal. A direct to metal cut is self explanatory, it is a recording cut direct to a metal disc from a cutting lathe that is used to stamp the vinyl. A lacquer disc is a metal disc covered in lacquer which is cut and used to create the metal disc that is used to stamp the vinyl. An acetate is the same as a lacquer disc except an acetate is the same size as a vinyl record, so it can be previewed before making the metal stamp disc. The more an acetate is played, the more the sound quality will decrease.
9. What information should be written on your master tapes?
The information written on a master tape should include the following: album title, artist, date, start ID's and tape number if applicable.
10. What is meant by multi-band compression?
Multi-band compression allows individual frequency bands of a signal to be compressed. Unlike conventional compression that compresses an entire signal. Multi-band compressors are generally used at the mastering stage of production.
11. Explain the term dynamic range.
Dynamic range describes the ratio of the softest sound to the loudest sound that can be played by an instrument or piece of equipment. Dynamic range measures the difference between the noise floor and the maximum output signal, this is measured in decibels. The human ear has a dynamic range of 120dB.
12. What is the formula for dynamic range?
The formula for dynamic range is DR = n + m. Where n = noise floor level in minus decibels and m = the peak level of decibels.
13. What is meant by SNR?
SNR is Signal to Noise Ratio or S/N. This is the difference between the noise floor and the reference level. This can sometimes be the same as the dynamic range.
14. Describe gain riding.
Gain riding is a recording term. It is where the gain level of a recording is constantly monitored and adjusted to prevent the signal overloading.
15. Comment on this article:
<http://www.digido.com/index/pmodule_id11/pmdmode=fullscreen/pageadder_page_id=93/>
Pay particular attention to what you feel about the subject. Essentially it is about where YOU stand on the subject within the big picture. For example are you joining the race or are you sitting on the fence? What would you do given the reins to a potential top ten album?
Don't understand this one, the link takes me to Digital Domain and the advertisement of a Mastering book. No article as such. 
16. What is meant by normalling?
Normalling (or normalizing) is the process where the EQ and the average level of the signal are 'evened out'. This process is meant to make the individual tracks of the song sit well together.
17. Explain DC offset
DC offset in the is an AC signal that is offset by a DC signal which is usually introduced through power supply interference. A signal that would normally have a peak of +3db and a valley of -3db with a +2db DC offset will have a peak of +5db and a valley of -1db. When a signal normally starts at zero crossing a DC offset will cause a click because of the sudden jump in amplitude.
18. How can the target audience affect mastering decisions?
The target audience has a big effect on how an album or track is mastered. Different musical genres require different mastering techniques, for instance a classical compilation would not be mastered in the same way as a dance compilation. A dance track will be 'loud and bright', whereas classical music changes volume frequently.
19. What happens to the audio signal when a aural enhancer is applied?
An aural enhancer uses processes that include dynamic equalisation, harmonic synthesis and phase manipulation to add high frequency harmonics to the signal. These harmonics are created from the original signal and reinforce the transient detail without significantly increasing the signal level.
20. What does relative loudness mean?
Relative loudness is how songs relate to each other regarding levels. For instance a soft ballad may have a higher average level than a loud rock song. Since it's the average level of a song that determines it's loudness, the soft ballad may sound louder than the rock song. This will cause a problem because it won't sound natural. All songs should relate to each other by having the proper relative loudness rather than the same average or peak level.
21. What does r.m.s. mean?
RMS stands for Root Mean Square. Square Root of the Mean (average) of the sum of the squares of each point on the waveform. This is a conventional way to measure audio signal voltage. Others ways include average volts, peak volts and peak-to-peak volts. Peak values are always higher, but RMS values are more accurate.
22. What is meant by 'entertainment quality'?
Entertainment quality is sound that is good enough for television, radio and other broadcasting mediums, but is not up to professional standard. Professional standard would be that which is sold ie. CD's.
23. What happens if you leave excessive, short transients in the music?
If excessive, short transients are left in the music this will cause an echo effect from neigbouring grooves when cutting vinyl. Or cause distortion of the sound.
Couldn't find very much info on this subject.
24. What is The K-System?
The K-system is a metering and monitoring standard that measures relative loudness. The K-system uses 0 dB as a reference loudness, which also determines the monitor gain. There are three different K-System meter scales, with 0 dB at either 20, 14, or 12 dB below full scale, for typical headroom and SNR requirements. The three K-System meter scales are named K-20, K-14, and K-12 surprisingly enough  . The K-20 meter is intended for wide dynamic range material like theatre and classical mixes. The K-14 meter is for productions intended for home listening, and the K-12 meter is for productions to be dedicated for broadcast.
Huzzah for Digital Domain!
25. What are The Equal Loudness Contours?
The Equal Loudness Contours are visual representations which demonstrate that the human ear does not hear all frequencies with the same sensitivity. This can be represented in graphical form which measures intensity in decibels and frequency in hertz, which creates contours. The human ear is most sensitive to frequencies around 2000Hertz and less sensitive to those that are higher or lower. This has particular significance when determining the optimum monitoring level of music in a studio environment.
26. What is MetaData?
MetaData is structured data that gives information about resources. It is sometimes referred to as 'data about data'. MetaData originally related to digital information used in databases, but is now understood to include any kind of descriptive information about resources whether digital or not. Examples are: library catalogues, an index in a book could be described as MetaData.
27. Explain the term Headroom.
Headroom is the difference between the nominal operating level and peak clipping, or maximum level. For example, a mixer operating with a nominal line level of +5dB and a maximum output level of +20dB has 15dB of headroom.
28. Explain the term Crest factor.
Crest Factor is the ratio of the peak value to the RMS (Root Mean Square) value. Musical signals can have peaks a lot higher than the RMS value. The larger the transient peaks, the larger the crest factor.
29. What skills and abilities must a Mastering Engineer possess?
A mastering engineer must have a musical as well as technical background, good ears and technical knowledge. Ideally, he/she should know how to read music, and have an excellent sense of pitch. It is expected that a mastering engineer will know how to use a wide range of specialized equipment which is used in the mastering studio, and must understand a range of musical styles and how best they sound.
30. What does the term “Masking” mean?
In simple terms, masking is where one sound is effectively 'covered' by another if they are at a similar frequency. A louder sound heard at one frequency prevents softer sounds near that frequency from being heard. Masking is used in noise reduction as it allows low-level noise to be masked by higher level signals of the music that are the same frequency.
31. Explain the Hass Effect.
The Haas effect describes the ear's perception to the direction a sound is coming from. If a sound is played to both ears at the same time at the same volume, it appears to be directly in front of us. But if the signal to one ear is delayed slightly, the sound appears to be coming from the other side.
32. Why is an acceleration limiter necessary in a vinyl cutting lathe?
An acceleration limiter is neccesary in a vinyl cutting lathe to fix problems in the recording such as vocal 'S' or half open hi-hats, that sound obnoxious on vinyl. When an acceleration limiter is triggered at the point when an "S" appears, they dump the whole top end. This has to be done only where necessary as having it switched on throughout will result in a record with no top end.
33. Explain, as separate paragraphs of up to 100 words, the two causes of mistracking of a vinyl record.
The first cause of mistracking of a vinyl record could be down to mechanical defects of the turntable that the record is being played on. Defects such as how the cartridge is aligned, how the tonearm is weighted. It could be 'wear and tear' of the needle that is causing mistracking. It could be that the cartridge outclasses the tonearm and therefore the tonearm can't handle what is being thrown back at it.
The second cause of mistracking of a vinyl record could be down to a worn or badly pressed record. If a record has not been pressed 'dead centre', when it is played on a turntable it will make the tonearm move from side to side which can cause mistracking. If a record is warped it will make the needle move up and down, which can cause it to lose contact with the record, causing mistracking.
34. Why is the bass on a vinyl record mixed into mono?
The bass on a vinyl record is mixed into mono because stereo low frequencies cause the stylus to move up and down and may lose contact with the record. This will make the groove disappear and cause mistracking. Bass has the largest amplitude on a record, therefore deep stereo bass is not possible as the groove will be too deep. The more stereo recorded the deeper the groove.
35. For maximum sound quality, what is the suggested duration of a single side of a vinyl record?
The duration of a 12" vinyl record is dependent on the volume, the depth and the amount of bass that is to be recorded. For low volume, shallow groove and low bass a 12" vinyl record can have 30 minutes of sound. Whereas high volume, deep groove and lots of bass will bring the time down to just 4 minutes. These values are recorded at 33 rpm.
36. What is a 'production master'?
A production master is the final copy of a project that will be used to create all other copies. It is the finished version ready for distribution. A production master can be any of the following formats: PCM-1630 tape, Sony 9000 cartridge, DDP Exabyte tape, and CDRs.
37. On a CD, what should the peak level be, at some point in the recording, in dBFS?
The peak level should be 0dBFS on a CD.
38. What is the maximum recommended duration of a CD?
The maximum recommended duration of a CD is 79 minutes 38 seconds for an 80 minute disc, and 74 minutes 30 seconds for a 74 minute disc.
39. Why is it possible for two recordings to differ in subjective loudness even if they peak at the same level?
It is possible for two recordings that peak at the same level to differ in subjective loudness because the human ear does not interpret loudness according to peaks. It judges the loudness by an average level of the signal.
40. List three methods of increasing subjective loudness.
Subjective loudness can be increased using compression, clipping or multi-band compression.
41. Briefly explain the function of a multi-band compressor
Unlike a conventional compressor that compresses the entire signal equally, a multi-band compressor allows you to set a frequency range for compression. Therefore the only part of the signal that is compressed lies between the lowest and highest frequencies that are set. |
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Sun Oct 31, 2004 8:52 am |
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AUdIoCoUrSeS
Joined: 31 Oct 2002
Posts: 2014
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| More input |
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Come in guys, before I comment we need more input from you all!
_________________
It's all in the ears. - Learn the concepts not the software.
Audio Courses is a way into the music business for you
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Mon Nov 01, 2004 11:05 am |
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seanm
Joined: 06 Sep 2004
Posts: 20
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| Week 8 - Mastering |
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sorry for delay chris should be fully up to date by sunday
subject:
1. What is Mastering?
Mastering is the last creative step in the audio production process. After mixing stereo mixes or sometimes stems (separate elements of a mix) are sent for mastering. Mastering provides the last opportunity to enhance the overall mix or repair problems caused during mixing. Mastering is the preparation of audio for playback on a wide range of playback devices. The main changes to a track during mastering are: tonal balancing and level adjustment. Tonal balancing through equalisation and level balancing through compression.
There are other effects/processors that can be used at the mastering stage for instance, audio enhancers, audio exciters and stereo expansion.
The steps taken in mastering a number of tracks are:
1. timeline all the tracks in the desired order. Leave a 2 second gap between tracks when producing a CD.
2. apply noise reduction to eliminate hum and hiss
3. normalize the tracks to set the highest peaks in audio volume to a preset level; the overall audio should never exceed 0 dBfs
4. equalize audio between two tracks to ensure there are no jumps in bass, treble, midrange, volume or pan
5. apply a compressor (for example, 4:1 starting at -6 dB) to compress the peaks but to expand the softer parts
6. apply a dynamics compressor to compress only specific frequencies that generate the audio peaks
7. in the case of mastering for broadcast, the bandwidth of the signal has to be reduced. For example for TV broadcast: apply a high pass filter at 80 Hz with -18 dB/octave to filter out low frequencies and apply a low pass filter at 12 kHz with -9 db/octave to filter out high frequencies
2. Why is mastering necessary?
Mastering is a specialist activity, mastering houses and mastering engineers are experts in their field. Mastering for different media takes particular skills and knowledge which most engineers and producers don’t necessarily have. Indeed it is not uncommon for producers to consult mastering engineers for their advice during recording sessions. Also if an albums tracks were recorded at different times and/or in different studios, they might not necessarily “sit” together very well without further processing. Mastering engineers can also provide a fresh set of ears to whom, the tracks sound new and fresh (they haven’t been living with the material for x months). Using their experience, purpose built studios with excellent acoustics and monitoring and their wide range of expensive equipment they should help to get the best possible sound.
3. What is Post Production?
Post production covers everything which happens to a mix after all recording and editing has finished. It includes all processing (noise reduction etc.) and submastering. Post production covers everything up to the actual duplication (vinyl, CD etc.) Even at the duplication facility further processing takes place.
4. Comment on “preparing your tapes”.
All tapes sent for mastering should be carefully labelled. Under no circumstances should these tapes be labelled “production master”, they are not. They should be labelled submaster or final mix or compiled mix.
Begin and end the reel with some “bumper”, followed by leader. If possible place leader between tracks. Tape should be slow wound, with tails out. Label with tape speed, record level for oVU in nw/M, record EQ, track configuration. Also whether it is mono, Stereo or multichannel. Indicate if noise reduction has been applied and if so include the noise reduction alignment tone. Include alignment tones (at least 30 seconds) of 1kHz, 10kHz, 15kHz and 100Hz plus 45Hz and 5kHz at oVU without noise reduction. It is also recommended by some that a tone sweep from 20 Hz through to 500Hz is provided. All these tones must have been recorded by the same tape recorder that recorded the music and ideally recorded through the same console and cables that where used to make the mix.
In addition particular where noise reduction might be required provide “handles” (a short section of background noise prior to the start and after the end) either side of the track.
5. Comment on “stereo bass”.
Too wide a stereo image on the bass make it difficult to cut with the desired volume and can make it impossible to cut the disc at all. In addition excessive stereo bass like any excessive stereo or out of phase information can cause overly deep grooves that waste space on the disc and are hard to fill on the pressing, increasing distortion and noise and decreased time.
6. Why is mono compatibility such an issue?
Many radio broadcasts are still received in mono and some club sound systems do not playout in stereo. Any phasing problems can cause “dropouts” in playback.
7. What is meant by the term “start ID”?
Start id is the marker, which should be placed on DAT masters at the start of each track.
8. What are the three types of Disc Cutting?
A “lacquer”, which is a lacquer coated aluminium disc. This is then coated in silver and put through a series of electroforming processes to produce successive metal-plated parts as follows: (Or in the direct metal mastering technique it is a copper coated disc, which bypasses some of the above electroforming processes.)
The Master, a negative with ridges in place of grooves.
The Mother, a positive
A Stamper, (a negative) this is the moulding tool to be used in pressing out records from thermoplastic vinyl.
9. What information should be written on your master tapes?
Label each reel with the album title, song titles, running times of each cut. Indicate tape speed; record level for 0VU in nw/M, record EQ (NAB or IEC) track configuration, and whether it is mono or stereo. Artist, Album title, record label, Reel number (including “of” how many if relevent), catalogue number, studio, address and contact number, engineer, assistant, producer, date. Additionally this should include format, EQ, speed, Level ( for instance ½” 2-track AES stereo no noise reduction, 30 IPS, 0VU=320nW/M, or 0VU=250 nW/M +2dB. Any test tones included, name of song/track, length, comments (e.g. “leave in cough at start” or “fart at end”) and name of next song etc.
10. What is meant by multi-band compression?
A multi band compressor is a compressor, which can act independently on user defined frequency ranges of a signal.
11. Explain the term dynamic range.
The ratio of the loudest (undistorted) signal to that of the quietest (discernible) signal in a unit or system as expressed in decibels (dB). Dynamic range is another way of stating the maximum S/N ratio. With reference to signal processing equipment, the maximum output signal is restricted by the size of the power supplies, i.e., it cannot swing more voltage than is available. While the noise floor of the unit determines the minimum output signal, i.e., it cannot put out a discernible signal smaller than the noise. Professional-grade analog signal processing equipment can output maximum levels of +26 dBu, with the best noise floors being down around -94 dBu. This gives a maximum dynamic range of 120 dB - pretty impressive numbers, which coincide nicely with the 120 dB dynamic range of normal human hearing (from just audible to uncomfortably loud).
12. What is the formula for dynamic range?
Max level(dB)-noise floor(dB)=dynamic range. (nDB = 20 log Eo/Ei where nDB the number of decibels corresponding to the voltage gain or loss, Eo = voltage output and Ei = voltage input.) ????
13. What is meant by SNR?
Signal to noise ratio is a specification for the level of noise produced by a system and is normally expressed in the decibel difference between the measured noise and some reference signal.
14. Describe gain riding.
Gain riding is a form of compression carried out manually. It refers to the technique of manually “riding the gain”, when a signal becomes too loud pull the fader down, when too low push the fader up. As such it requires intimate knowledge of the signal.
15. Comment on this article:
http://www.digido.com/index/pmodule_id=11/pmdmode=fullscreen/pageadder_page_id=93/ Pay particular attention to what you feel about the subject. Essentially it is about where YOU stand on the subject within the big picture. For example are you joining the race or are you sitting on the fence? What would you do given the reins to a potential top ten album?
The article makes a convincing case that the “loudness war” is having a detrimental effect on music. It claims that the louder the CD the less transient clarity and dynamic range the music will have. Since I think that the music is the most important thing, I find this disappointing. The blame for this seems to be laid at the door of record companies and artists (perhaps to a lesser extent), with the engineer’s presented as the voice of sanity and reason. The record buying public seemingly the ignorant bystanders who despite their remote controls are perceived to be incapable of making alterations to volume between CD’s. The article is suggesting this is all getting out of control and a radical rethink is required. At this stage I am inclined to agree with them, but feel sure that if I was employed to master a potential top ten album and asked to make it loud at the expense of quality, I’m sure I would.
16. What is meant by normalling?
Normalising is a method of increasing the level of a signal based on its relative level. Normalising searches the signal for the loudest peak and then increases the level of the whole signal so that the loudest peak reaches either digital full scale or a level set by the user.
17. Explain DC offset
DC offset occurs when hardware, such as a soundcard, adds DC current to a recorded signal. This current results in a waveform that is not centred around infinity (the average between the positive and negative peaks in the wave). Although it is inaudible it will degrade a compressed file and add distortion if other filters are applied to the uncorrected wave.
18. How can the target audience affect mastering decisions?
The target audience or intended market for a recording has an enormous impact on mastering decisions. For instance a dance record might be excessively compressed whilst such compression would be wholly inappropriate for classical music.
19. What happens to the audio signal when an aural enhancer is applied?
Aural enhancers create new high frequency harmonics in a sound. This is known as harmonic synthesis. Aural enhancers send some dry sound to a side chain highpass filter. The output of the highpass filter is processed dynamically to add phase shift and create synthesised high frequency harmonics. Adding a small amount of this carefully controlled distortion can make the sound quality appear cleaner and more detailed.
20. What does relative loudness mean?
Relative loudness refers to the mastering technique of adjusting the average level (which determines a tracks perceived loudness) of each track on a master so that volume changes are not necessary between tracks on playback.
21. What does r.m.s. mean?
RMS : Root Mean Square. A formula for describing the level of a signal. RMS is derived by squaring all of the instantaneous voltages along a waveform, averaging the squared values, and taking the square root of that number.
22. What is meant by 'entertainment quality'?
Entertainment quality or broadcast quality refers to the quality of production necessary for braodcast on TV or Radio.
23. What happens if you leave excessive, short transients in the music?
Short transients are caused by short usually percussive sounds, they do not appear loud to the human ear because of the time taken by the human ear to process them their loudness makes them seem less loud than longer signals. Leaving excessive short transients in the music will result in a reduction in available dynamic range and pushes the whole signal closer to the noise floor. Controlling these transients enables the whole signal to be raised.
24. What is The K-System?
The K system has been developed by Bob Katz, Bob’s proposal is a metering and monitoring standard that integrates the “best” concepts of the past with current “psychoacoustic” knowledge in order to ameliorate the chaos of the last 20 years. In the K System relative loudness is referenced as 0dB. In addition he wants this 0dB to determine monitor gain, this he says will encourage us all to concentrate on the message rather than the medium. The resulting dual meter system has a bar representing the average level and a moving line or dot representing the most recent highest instantaneous (1 sample) peak level.
Using pink noise to calibrate electrical levels the full digital scale will always be at the top of each K system meter. Naturally this means the 83 dB SPL point will slide relative to the maximum peak level and using the K-(N) simultaneously defines the meters 0dB point and the monitor gain.
The peak and average scales are calibrated as per AES-17, so that peak and average sections are referenced to the same decibel value with a sine wave signal. In other words, +20 dB RMS with sine wave reads the same as + 20dB peak. Analogue voltage level is not specified in the K-system, only SPL and digital values. There is no conflict with -18 dB FS analogue reference points commonly used in Europe.
The K System has three different applications:
The K20 meter is intended for wide dynamic range material, e.g., large theatre mixes, "daring home theatre" mixes, audiophile music, classical (symphonic) music, "audiophile" pop music mixed in 5.1 surround, and so on.
The K-14 meter is for the vast majority of moderately-compressed high-fidelity productions intended for home listening (e.g. some home theatre, pop, folk, and rock music).
The K-12 meter is for productions to be dedicated for broadcast.
The numbers 20-14-12 refer to dB below full scale (0dB) for typical headroom and SNR requirements. Please remember people that full scale digital is always at the top of each K system meter.
25. What are The Equal Loudness Contours?
The human ear is not equally sensitive to all frequencies, particularly in the low and high frequency ranges. The ears’ response to frequencies over the whole range was originally charter by Fletcher and Munson (1933). Later research led to a set of curves showing the sound pressure levels of “pure tones” that are perceived as equally loud. These curves (contours) are plotted for each 10dB rise in level with a reference tone at 1kHZ. The curves are lowest in the range from 1-5kHZ, with a dip at 4kHZ, indicating that the ear is most sensitive to frequencies in this range. The intensity level of higher or lower tones must be raised substantially in order to create the same impression of loudness. The Phon scale was devised to express this subjective impression of loudness, since the dB scale alone refers to the actual sound pressure or intensity level.
26. What is MetaData?
MetaData is data encoded with an audio signal, which is not audio but information about the audio e.g parameters which apply globally to a particular data transmission, as opposed to the data actually carried in the transmission. This can be used to store information such as: markers (soundforge), bit rate and copyright information.
27. Explain the term Headroom.
Headroom is the amount of additional signal above the input level that can be sent into a system before “clipping” distortion occurs.
28. Explain the term Crest factor.
Crest factor is the ratio between the average amplitude as shown on a VU meter and the instantaneous amplitude as shown on a peak meter.
29. What skills and abilities must a Mastering Engineer possess?
Mastering engineers need a complex mixture of technical knowledge/experience and artistic feeling for the music and what it is trying to achieve. They need to understand the needs of their clients, the requirements of different duplication and broadcast media and the sensibilities of the market place.
30. What does the term “Masking” mean?
Masking occurs when one sound appears to make another sound inaudible. With frequency masking this can occur when sounds of very similar frequencies occur together. This is because the human ear tends to blend these sounds together.
31. Explain the Hass Effect.
The Haas effect refers to the brains ability to integrate incident sound and early reflections into a single sound. Those early arrivals which occur within the first 5-35ms, that are not more than 10dB louder than direct sound will be combined and added to the first arrival and localised to its source. If the delayed sound is more than 10dB louder or the delay is greater than 35ms, the listener will perceive distant echoes.
32. Why is an acceleration limiter necessary in a vinyl cutting lathe?
An acceleration limited is designed to protect the cutting head and make the groove cut more managable. Helium is fed to the cutting head to prevent overheating during loud, bright passages.
33. Explain, as separate paragraphs of up to 100 words, the two causes of mistracking of a vinyl record.
Mistracking can occur if the groove of the record becomes too shallow. Stereo record use a “v” shaped groove in which one “wall” carries the left signal and the other carries the right signal. If the input signal is mono, or does not have a great deal of stereo content the result will be a groove that only moves from side to side, the vertical component will be zero. This can result in a shallow groove, which leaves the stylus with nothing to track and will slide into the next groove.
Due to the mechanical nature of the groove-disc system, a playback stylus never maintains perfect contact with a modulated groove, but is constantly losing and regaining contact with one groove wall and then the other. Each time it regains contact, it puts a small click into the signal, resulting in every amplifier stage acting to generate energy from this. A short click contains a large amount of ultrasonic energy (a pulse 1ms long has a flat frequency content to almost 1MHZ). Non linealities in amplification stages cause this high frequency content to intermodulate with signal frequencies to produce sum and difference components: the “difference ones causing “splatter” sounds in the audible range. This is the source of mistracking, an overlay of harsh, fuzz or airiness in the signal.
34. Why is the bass on a vinyl record mixed into mono?
To avoid cutting problems and increase it’s relative volume (panning law). This will also alleviate mistracking problems and maximise the records’ duration and loudness.
35. For maximum sound quality, what is the suggested duration of a single side of a vinyl record?
A 12 inch vinyl record at 33rpm has a playing time between 15 and 30 minutes depending on how heavily the signal has been modulated and the amount and character of its bass content.
36. What is a 'production master'?
A Production master is the name given to the stereo mix which, leaves the mastering studio for duplication.
37. On a CD, what should the peak level be, at some point in the recording, in dBFS?
dBFS = dB relative to Full Scale, i.e. the indicated maximum peak record level as indicated by the level meter of a digital audio workstation, DAT recorder or CD recorder. The peak level on a CD should not exceed 0dBFS.
38. What is the maximum recommended duration of a CD?
The final CD Master tape, including songs, spaces between songs, and reverberant decay at the ends of songs, must not exceed 79:38.
39. Why is it possible for two recordings to differ in subjective loudness even if they peak at the same level?
Two recording might differ in subjective loudness even if they peak at the same level because the human ear does not interpret loudness according to its peak, but by the average level of the signal.
40. List three methods of increasing subjective loudness.
Compression
Simultaneous Normalising/limiting (waves L1)
Parametric EQ (Smile Curve). (Exploiting fletcher Munson curves)
41. Briefly explain the function of a multi-band compressor
The function of a multi band compressor is to compress separate frequency ranges in a signal independently. This can be used to apply compression to low frequencies while having no impact on mid and higher frequencies. Multiband compression can also be used as a method of increasing subjective loudness. |
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Fri Nov 05, 2004 1:52 pm |
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