Acoustics

Using any of the resources below to gain a thorough understanding of the following terms (including how they relate to each other): sound waves, frequency, amplitude, phase, sine-tone, noise, fundamental, overtones, spectrum, partials, standing waves, waveform, fourier analysis, spectrogram, formant, amplitude envelope (and loudness), timbre.

You should be able to:

• explain the difference between harmonic and inharmonic spectrum;

• explain what white noise and pink noise are;

• apply the above terminology to characterise sounds;

• understand frequency and time domain representation of sound;

• explain how/why playing harmonics on a guitar works.

Look at the quiz page, to test your knowledge.

You should also be able to use SPEAR (or a similar tool) to:

• generate a spectrogram from a given sound;

• identify partials in the sound (if there are any);

• find different ways of changing the timbre of a sound without changing its pitch.

• transform a harmonic sound into an inharmonic one.

• add vibrato to a sound.

An MA thesis on the use of spectral manipulation for sound design including explanations of some of the techniques and their implementation.

Stockhausen's piece Stimmung is based on the ability of vocalists to emphasise overtones of the harmonic series.

Resources:

Physclips * acousticslab * Handbook of Acoustic Ecology * physics and psychophysics of sound and hearing * Acoustics from Santa Fe University of the Arts.

An excerpt from Pierre Schaeffer's Solfege de l'object sonore illustrates the complexity of timbre perception:

Some refinement about the notion of pitch:

• Periodic waveform results in pitch sensation. Explore how many repetitions of the waveform are needed to produce identifiable pitch.

• The phenomena of the missing fundamental, and an illustration of masking the tones with noise bands.

• The endless glissando (and read about Shepard tones).

• Repetition of noise can produce pitched sounds (listen to the 'Pitch and Infrapitch' examples).

There is also some interaction between sonic parameters:

• Effects of duration on loudness.

• Loudness can effect our perception of pitch.

And there is also interaction between visual and auditory perception:

Our ability to analyse sound into its time-frequency components allowed researchers at IEM to create a speaking piano (controlled through pure data).