• Digital Recording Theory• Using Peak

Listening

James Tenney, Collage #1 (“Blue Suede”), 1961. Available in Bracken Library, on James Tenney

Selected Works, or on the listening list for the first quiz.

Listening List

The Listening List is available on the course website, with links to mp3 files:http://kkothman.iweb.bsu.edu/listening140.htm

Be able to identify each work by title, composer, and year composed.

Listening quiz will be part of first quiz, 1/31.

Digital Recording Theory: Sample Rate Sample Rate (SR) is the rate at which the amplitude of the

signal is sampled, or measured. SR dtermines the maximum frequency that can be represented

accurately. Nyquist Frequency: one-half the SR, which represents the

highest frequency that can theoretically be represented accurately. Since audio signals have a positive and negative amplitude

fluctuation within one cycle, you must measure at least twice per cycle to accurately represent the frequency.

Frequencies above the Nyquist will be aliased. However far a frequency is above the Nyquist, it will be represented

as being that far below the Nyquist. This is the same effect as car wheels appearing to move

backwards on film.

Digital Recording Theory:Bit Resolution Bit Resolution determines the amplitude resolution,

or how accurate the measurement of amplitude will be for each sample taken. One bit provides only two possible values for amplitude. Two bits provides four possible values. (etc.)

Any amplitude not accurately represented will result in some error, which in the audio domain is noise.

Each added bit increases the Signal-to-Noise Ratio by approximately 6 dB. The S/N ratio represents the difference between the

maximum amplitude that can be represented, and the noise floor of the system.

CD Quality vs. Higher Definition formats CD = 44.1 kHz SR and 16 bit resolution.

Nyquist = 22.05 kHz max f 96 dB S/N maximum (6 db per bit)

Human hearing range. Added bits (24 bit) more noticeable than higher sampling

rates. Higher sampling rates can’t extend our hearing range,

but because we’re more sensitive to time differences than frequency, they can provide greater clarity in representing transients and provide clarity to the mix. (“air”)

Dither

At low amplitude levels, the ADC process can involve the turning on and off of a single bit, leading to a square wave representation of the sound. (adding high harmonics not present in the original signal)

Low-level Quantization noise Dither involves adding analog noise to the signal

prior to ADC, causing the ADC to make random variations at low levels, and eliminating most of the harmonic distortion.

Representation of Sound

Sound is a time domain phenomenon. Graphic representations of sound can only

focus on one parameter.Most commonly, graphic representations

focus on amplitude in a particular domain: Time domain: amplitude over time Frequency domain: amplitude over frequency

Learning Software

Don’t avoid the manual!PDF versions of most manuals are

available on the musictechxserve. (connect to the “manuals” directory at login)

Learn to use the index.Consider working through tutorials if

available.

Creative Project Assignment

Assignment 1 due 1/31Sounds available on the musictechxserve

Peak

Demonstrated in Class

Reading Assignment (due 1/24)

“Introduction” to Part I: Theories, in Audio Culture, including the two gray pages of quotes immediately before it. (pp. 3 - 6)

Attali, “The Politics of Noise” (pp. 7 - 9)Varese, “The Liberation of Sound” (pp. 17

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