Digital Sound & Music: Concepts, Applications, & Science, Chapter 2, last updated 6/25/2013

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response graph that shows the phase that each frequency component is in. Each of these two

graphs covers the audible spectrum. In Section 3, you‟ll be introduced to the mathematical

process – the Fourier transform – that converts sound data

from the time domain to the frequency and phase domain.

Applying a Fourier transform to impulse response data –

i.e., time represented in the time domain – yields both

frequency and phase information from which you can

generate a frequency response graph and a phase response

graph. The frequency response graph has the magnitude

of the frequency on the y-axis on whatever scale is chosen

for the graph. The phase response graph has phases

ranging from -180 to 180 on the y-axis.

The main points to understand are these:

A graph is a visualization of data.

For any given instance of sound, you can analyze the data in terms of time, frequency, or

phase, and you can graph the corresponding data.

These different ways of representing sound – as amplitude of sound over time or as

frequency and phase over the audible spectrum – contain essentially the same information.

The Fourier transform can be used to transform the sound data from one domain of

representation to another. The Fourier transform is the basis for processes applied at the

user-level in sound measuring and editing software.

When you work with sound, you look at it and edit it in whatever domain or

representation is most appropriate for your purposes at the time. You‟ll see this later in

examples concerning frequency analysis of live performance spaces, room modes,

precedence effect, and so forth.

2.2.6 Ear Testing and Training

If you plan to work in sound, it‟s important to know the acuity of your own ears

in three areas – the range of frequencies that you‟re able to hear, the differences

in frequencies that you can detect, and the sensitivity of your hearing to relative

time and direction of sounds. A good place to begin is to have your hearing

tested by an audiologist to discover the natural frequency response of your ears.

If you want to do your own test, you can use a sine wave generator in Logic,

Audition, or similar software to step through the range of audible sound

frequencies and determine the lowest and highest ones you can hear. The range

of human hearing is about 20 Hz to 20,000 Hz, but this varies with individuals

and changes as an individual ages.

Not only can you test your ears for their current sensitivity; you also can train your ears

to get better at identifying frequency and time differences in sound. Training your ears to

recognize frequencies can be done by having someone boost frequency bands, one at a time, in a

full-range noise or music signal while you guess which frequency is being boosted. In time,

you‟ll start “guessing” correctly. Training your ears to recognize time or direction differences

requires that someone create two sound waves with location or time offsets and then ask you to

discriminate between the two. The ability to identify frequencies and hear subtle differences is

Max Demo:

Ear Training

for

Frequencies

Aside: WAV and AIFF files

store audio as amplitude

information in the time domain,

while MP3 files store audio as

spectral data in the frequency

domain. Both methods are able

to capture the sonic information

for playback later on.