d. The measurement characteristics of a sound wave, having been explained, need to be
understood more clearly. Some of these characteristics are interrelated and affect hearing.
(1) An immediate relationship occurs between the number of cycles per second (frequency)
of a sound wave and its physical length, or wavelength. One wavelength equals the length in space (or
in any given medium) occupied by one cycle of the wave. If the frequency doubles, then one cycle or
one wavelength occupies one half as much space. The higher the frequency, the shorter the wavelength;
the lower the frequency, the longer the wavelength. Frequency also determines pitch. The subjective
aspect of frequency, pitch, determines its position in the musical scale heard by the ear. The frequencies
audible to human hearing ranges from approximately 15 Hz to 20,000 Hz, the audio spectrum.
(2) Amplitude determines the intensity or power of a sound. Increasing the amplitude or
height of a wave increases its intensity or power and the violence by which the molecules collide with
each other in the medium. The ear responds to this by "hearing" the sound as being louder.
e. Sound consists of more than what has been discussed so far. Sounds occur continuously
every day: people talking, dogs barking, the sounds of cars passing by, music from radios, etc. All of
these make up sound waves called complex waves. Complex waves consist of a multiple of frequencies
which can be broken down into three components: a fundamental, harmonics, and overtones.
(1) The fundamental frequency, the lowest frequency of the complex wave, determines the
pitch of a musical note.
(2) Harmonics. Any frequency that is an odd multiple of the fundamental frequency, such as
1, 3, or 5 times the fundamental frequency.
(3) Overtones. A harmonic of the fundamental frequency of a complex waveform.
Learning Event 3:
DESCRIBE FACTORS AFFECTING SOUND QUALITY
1.
When a sound wave travels through a medium such as air and encounters another medium such
as water, colder air, or a solid object, part of the sound is reflected back from the object in a manner
similar to a beam of light. The balance of the sound passes into and is transmitted by the second
medium.
a. Reflection. If the sound wave strikes a hard surface at an angle, a large part will bounce off
and be reflected at an angle which is exactly equal to the angle of incidence (fig 1-12). Reflected sound
increases the intensity, causing a type distortion by adding an echo (a reflected sound) or reverberation
(a multiple reflection of sound). Large areas with hard surfaces, such as auditoriums, produce a lot of
reverberation and echo. The shape and size of the area also determines the reflection of sound. Large
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