Hearing Science

sound waves consist of

Compression and rarefactions that repeat in a cyclic way

Frequency

How many cycles happen in 1 sec measured in Hz or kHz

Period

Time duration of a single cycle of a wave measured in milliseconds

Wavelength

Spatial distance between equivalent points on a wave measured in Meters or cm

Sine tones

based on a circle and can be combined to create more complex tones, can either amplify or cancel out sound when doubled

Fourtier Analysis

Used to understand complex sounds in terms of their sine wave components that differ in frequency, amplitude and phase

Phase

Where a sine wave is at a point in time in degrees

Waveform (temporal domain)

amplitude/pressure changes overtime

Spectrum

amplitude/level changes over frequency

Spectrogram

Changes in the spectrum overtime

Periodic sounds

sounds that repeat with the same regularity continuously

Non-periodic sounds

Sounds that do not repeat (white noise)

Line Spectra

Simple or complex tones that repeat are represented by this

Filters

Allows some frequencies to pass through but reduces the amplitude of others

Lowpass Filter

Frequencies below the cutoff point pass through

Highpass Filter

Frequencies above the cutoff point pass through

Bandpass filter

frequencies between two cutoffs pass through

Formants

Broad band of energy on the spectrum define different vowels acoustically

Vocal Tract

Acts like a complex band of filters increasing and reducing the amplitude of different frequencies

Digital signal processing

In digital audio higher resolution sound has more pixels, columns and rows

More Columns=

Higher sampling rate and the ability to capture more rapid changes overtime

More Rows=

Higher bit depth and finer distinctions in level

How much resolution is enough?

We need twice the sampling rate to digitally represent a given frequency

Nyquist Frequency

is equal to the sampling rate divided by 2

Higher bit depth

allows many possible levels of amplitude