Consumer Audio formats

Consumer Technology Formats

• Vinyl

• Cassette

• CD

• Compressed Digital Formats

Vinyl

• First popular in 1950s but still in demand today

• Many vinyl records have become collectable items and some limited-edition records are worth a lot

• Pressing a record involves engraving a copy of an acoustic waveform onto vinyl

• A stylus then moves in a groove as the disc is rotated. The vibrations are converted into an electrical signal

• Each side of the groove corresponds to a separate signal to create a stereo image

• Record labels continued to release records in both mono and stereo in the 60s as stereo did not becume standard until later in the decade

• Low frequencies have to be reduced on th record to prevent the stylus from moving too much, and so EQ is applied when playing a record back to return the frequencies to the correct level.

• Records were payed at different speed, measured in RPM (Revolutions per minute) depending on size

• 12” LPs where played at 33 1/3 RPM

• Singles were at 45 RPM

• Early shallac records released up until the mid 50s at 78RPM

Vinyl - Advantages

• Enthusiasts argue that records sound authentic / warmer

• Some DJs still use vinyl records to beat-match and scratch

• There has been a recent resurgence in the popularity of vinyl

• Bands sometimes release vinyl for kudos

• Record sleeve artwork is still appreciated by many fans

Vinyl - Disadvantages

• Sound quality can deteriorate towards the record’s centre becouse of the turntable’s constant rotation speed

• Not very portable

• Easy to scratch, which causes needles to jump

• Dust affects the sound, causing crackle; this is unfortunate as vinyl creates a static charge which attracts it

• Prone to warping if exposed to heat

• Prone to rumble at less than 30Hz.

Cassette

• FIrst popular in 1970s

• Use the same technology as studio multitrack tape, but minaturised and with fewer tracks

• Particles of iron oxide on the surface of the tape are magnetised by the signal from the recording head of a tape recorder. The polarisation of these particles represents the audio signal

• The playback head ‘reads’ the magnetic information and coverts it back into and electrical signal for amplification

• Erase head of a tape recorder uses a strong permanent magnet that is placed near the tape to reset the polarisation of the iron oxide particles.

Cassette - Advantages

• Initially cheaper than vinyl, but now more expensive due to lack of demand

• Difficult to scratch or damage the surface of tape as it is protected in a case

• Easy to copy with ‘high speed dubbing’

• Longer recording times than vinyl LPs

• More portable than vinyl records

Cassette - Disadvantages

• Sometimes get tangled or snap; this can damage the tape and cause loss of parts of the audio

• Recorders need to be cleaned with a head cleaner cassette as the oxide had a tendancy to rub off the tape

• Quality of recording degrades with each playing, and if stored in strong magnetic fields

• Susceptible to hiss, hence the noise reduction technologies developed by Dolby and dbx

• Wow and flutter occurred with small variations in moter speed causing variations in pitch

• Prone to print through, the music is heard as an acho before it actually plays.

CD

• CD stands for ‘Compact Disc’

• It is an optical disc that stores data as pits on a disk read by a laser

• CDs can hold 74-80 minutes of stereo LPCM audio (at 16 bit / 44,100Hz)

• They can also store up to 700mb of data

CD - Advantages

• Better signal-to-noise ratio than tape or vinyl, with a wider dynamic range

• Don’t degrade with mulitple playings

• Cheaper to manufacture than tape and vinyl

• Better frequency response

• Quick and easy access to tracks because of track indexing

• Easy to transfer music from CD to computer

• Longer playing time and more portable than vinyl records

CD - Disadvantages

• Scratching can cause issues with a large amount of data and render sections of discs unplayable

• Some analogue enthusiasts consider the sound of CD as ‘brittle’ and ‘unmusical’, preferring the warmth of vinyl.

Compressed Digital Formats (Lossy)

• Since late 90s, compressed digital audio formats have become more prevalent

• MP3 encoders compress audio data very effectively, significantly reducing the file size when compared to an uncompressed audio file

• There is a pay-off in terms of frequency content and dynamic detail, some of which is lost

• Audible when listening to MP3s through higher quality speaker systems

• In early 2000s, better file compressio formats, such as MP4 / AAC, offered an improvement sound quality over MP3, and are used by iTunes and otehr online music platforms.

• These files are still compressed and thus are not as good as CD quaility and WAV files, but many listeners are willing to make the trade-off considering compressed digital audio’s convenience, file size and portability

Lossy audio compression reduces the file size by losing some frequency content and dynamic detail. Lossless audio files are larger than lossy ones, but when uncompressed, the digital data is the same. This functions in a similar way to to storing documents in a compressed zip file, although the documents take up less space, and no information is lost during the compression process.

Compressed Digital Formats - Advantages

• Easy to share, you can attach compressed digital audio files to an email or share using cloud services, due to its small file size

• Easy to buy or stream albums - this can be done at the push of a button

• Lossless compression does not lose any digital audio data

Compressed Digital Formats - Disadvantages

• Lossy formats - this is when some audio data is lost while being encoded. This can cause issues with the stereo field on a recording and mask effects, whilst also introducing unwanted artefacts onto the track. Lossy formats can also have increased noise and an uneven frequency response. High frequencies are sometimes reduced depending on the format.

• Lack of ‘physical’ product and album artwork

• Digital data is easy to copy and thus copied or shared audio files can affect a musician’s income.

Comparing compressed to uncompressed digital audio

• Bit rate of CD audio is just over 1411kbps (kilobits per second)

• MP3 bit rates range from 96kbps to 320 kbps - which shows the amount of data compression that has taken place in comparison to CD audio

Types of digital formats

• MP3 - MPEG Layer III file - historically the most common format for compressed digital audio

• WMA - Windows media audio - proprietry alternative to MP3

• AAC - Advanced audio coding - Lossy - used by iTunes with ‘m4a’ as an extension

• OGG (Ogg vorbis) - alternative to MP3 used by Spotify

• ALAC (Apple lossless audio codec) - Also used by iTunes with ‘m4a’ as an extension

• FLAC (Free lossless audio codec)

Online streaming services

• Gained increased popularity in recent years - key way that music is listened to

• Had an impact on other areas of the music business with artists receiving less money for streaming music compared to singles and album sales

• Stream compressed audio so quality is not as good as CD.

• Very convenient and portable and most can’t hear the difference

• Normal bit rate is at 96kbps - sounds fine on earbuds on bus but will be noticeable on high-quality systems

• High bit rate is 160kbps

• Very high bit rate is 320kbps

• Producers are now mixing and mastering with online streaming in mind.

• Many online streaming services add extra processing to music i.e. volume normalisation and limiting.