Dog Whistle and Hearing
Name: Errol M.
Date: April 2002
When you blow through a "silent" dog whistle, what sound
level in decibels, is the dog hearing?
It is necessary to distinguish between the intensity of the sound, which
is a measure of the acoustic power of the sound wave, and loudness of a
sound, which is the range of frequencies and sound intensity that the human
ear can process.The former is strictly physics; the latter is physics plus
physiology of the ear.
The 'bel' is the fundamental unit of sound intensity. It is defined as the
log(base 10) of the ratio of the power:1 bel = log(P2/P1). A decibel,db, is
1/10 of a bel. So the decibels is a relative measure of power. In turn,
power is defined as energy/time*area^2 = ergs/sec*cm^2.
The loudness of a sound is measured in 'phons', which is defined as
numerically equal to the sound intensity in 'db' relative to a sound
pressure 0.0002 dynes/cm^2 of a single frequency of 1000 cycles/sec.
Problem is we don't know what dogs can hear. Humans hear frequencies
between about 20 cycles/sec to 20,000 cycles/sec at 130 db (very loud). This
shrinks to a range of about 700 cycles/sec to 6000 cycles/sec at 0 db(very
Even for humans these limits are quite variable, and I presume they
would be for various dogs too. Measurements of physiological responses to
sound (or light) are very difficult and complicated to quantify.
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Update: June 2012