5.19 Human Hearing
163
6.0
5.4
4.8
4.2
3.6
3.0
2.4
1.8
1.2
0.6
0.0
0.0
4.8
9.6
14.4
19.2
24.0
Time (sec)
Frequency (kHz)
Fig. 5.18 Humpback whale voice print
instrument player. Involuntary quavering of the voice is indicative of tremors,
brought on by heighten psychological responses or by neurological pathologies.
• Beats: Suppose two sinusoidal waves with the same amplitudes but slightly
different frequencies, f 1 and f 2 , are made to interfere. The result will be a wave
which has a wavering amplitude of frequency |f 2 − f 1 |. For example, with two
audible sounds of frequency 440 and 442 Hz, one can hear a very low variation
in intensity with a frequency of 2 Hz. One says that the two waves are ‘beating’
against each other, with a result that you hear ‘beats’. The effect demonstrates
the principle of superposition of waves.
• Modulation: Varying the amplitude (AM) or frequency (FM) of a given wave,
called the ‘carrier’
• Masking: The perceptional loss in hearing the fundamental of a sound when that
sound has strong harmonics
• Aural Illusion: The human brain’s re-interpretation of sounds which may not be
present; evident when a small speaker plays music with little or no fundamental.
The brain’s auditory interpreter tends to add the low note in the sounds from a
small speaker when it expects to hear one.
• Phoneme: Short distinguishable audible sound used to make up speech
• White Noise: Sound with the presence of a full spectrum of frequencies with
intensities and phases which vary quasi-randomly over the spectrum and over
time. Quasi-randomly distributed tones occurring at unpredictable times produce
what is now called ‘white noise’, the term white borrowed from a similar
163
6.0
5.4
4.8
4.2
3.6
3.0
2.4
1.8
1.2
0.6
0.0
0.0
4.8
9.6
14.4
19.2
24.0
Time (sec)
Frequency (kHz)
Fig. 5.18 Humpback whale voice print
instrument player. Involuntary quavering of the voice is indicative of tremors,
brought on by heighten psychological responses or by neurological pathologies.
• Beats: Suppose two sinusoidal waves with the same amplitudes but slightly
different frequencies, f 1 and f 2 , are made to interfere. The result will be a wave
which has a wavering amplitude of frequency |f 2 − f 1 |. For example, with two
audible sounds of frequency 440 and 442 Hz, one can hear a very low variation
in intensity with a frequency of 2 Hz. One says that the two waves are ‘beating’
against each other, with a result that you hear ‘beats’. The effect demonstrates
the principle of superposition of waves.
• Modulation: Varying the amplitude (AM) or frequency (FM) of a given wave,
called the ‘carrier’
• Masking: The perceptional loss in hearing the fundamental of a sound when that
sound has strong harmonics
• Aural Illusion: The human brain’s re-interpretation of sounds which may not be
present; evident when a small speaker plays music with little or no fundamental.
The brain’s auditory interpreter tends to add the low note in the sounds from a
small speaker when it expects to hear one.
• Phoneme: Short distinguishable audible sound used to make up speech
• White Noise: Sound with the presence of a full spectrum of frequencies with
intensities and phases which vary quasi-randomly over the spectrum and over
time. Quasi-randomly distributed tones occurring at unpredictable times produce
what is now called ‘white noise’, the term white borrowed from a similar