10.3 characteristics of a sound wave (ESADD)

Since sound is a wave, we deserve to relate the nature of sound to the nature of a wave. The basic properties that sound are: pitch, loudness and also tone.

You are watching: The pitch of a sound is determined by


Figure 10.2: Pitch and loudness that sound. Sound B has actually a lower key (lower frequency) 보다 Sound A and also is softer (smaller amplitude) than Sound C.


The frequency that a sound wave is what her ear understands together pitch. A higher frequency sound has actually a greater pitch, and also a reduced frequency sound has a reduced pitch. In figure 10.2 sound A has actually a greater pitch than sound B. Because that instance, the chirp of a bird would have actually a high pitch, but the roar of a lion would have actually a low pitch.

The human being ear have the right to detect a wide selection of frequencies. Frequencies from 20 to 20 000 Hz room audible come the human ear. Any sound with a frequency listed below 20 Hz is well-known as an infrasound and also any sound through a frequency over ( ext20 000) ( extHz) is recognized as one ultrasound.

Table 10.2 lists the ranges of part common pets compared to humans.

lower frequency (( extHz)) upper frequency (( extHz))
Humans ( ext20) ( ext20 000)
Dogs ( ext50) ( ext45 000)
Cats ( ext45) ( ext85 000)
Bats ( ext20) ( ext120 000)
Dolphins ( ext0,25) ( ext200 000)
Elephants ( ext5) ( ext10 000)

Table 10.2: selection of frequencies

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Range of wavelengths

Using the information given in Table 10.2, calculation the lower and also upper wavelengths the each species can hear. Assume the speed of sound in wait is ( ext344) ( extm·s$^-1$).


The amplitude of a sound wave determines that loudness or volume. A bigger amplitude method a larger sound, and a smaller amplitude method a softer sound. In figure 10.2 sound C is louder than sound B. The vibration of a source sets the amplitude the a wave. That transmits energy into the medium through the vibration. An ext energetic vibration coincides to bigger amplitude. The molecules move earlier and forth more vigorously.

The loudness the a sound is additionally determined by the sensitivity the the ear. The human being ear is much more sensitive to part frequencies than to others. The volume us receive thus depends on both the amplitude that a sound wave and whether that is frequency lies in a region where the ear is an ext or much less sensitive.

Sound, frequency and amplitude

Textbook exercise 10.1

Study the following diagram representing a musical note. Redraw the diagram for a note

with a higher pitch

that is louder

that is softer


Solution no yet available

Comparing sound generating instruments

The size and shape the instruments impacts the sounds that they are able to produce. Uncover some instruments that have various physical characteristics and also compare their sounds. You could:

Option 1: Vuvuzelas:

Compare the sound made through blowing through vuvuzelas of various sizes. Friend will need to find a couple of different vuvuzelas. Take turns blowing the different ones, one at a time and record which you think is louder (amplitude), i m sorry is of higher pitch (frequency).

Option 2: Tuning forks:

Compare the sounds developed by tapping tuning forks of different sizes.

You will need to uncover a few different tuning forks. Take transforms tapping the different ones, one in ~ a time and also record which girlfriend think is enlarge (amplitude), i m sorry is of greater pitch (frequency).

Option 3: Signal generator and oscilloscope

Use a function generator linked to a speak to develop sounds of various frequencies and also amplitudes and also use a microphone associated to an oscilloscope to display screen the characteristics of the various sounds produced.

Function generator

The function generator permits you to manage the loudness and also frequency that the sound being produced by the speaker. The will have controls because that amplitude and frequency.

A duty generator



The microphone have the right to then pick up the sound and also convert it come an electrical signal which can be displayed on the oscilloscope.

The most usual oscilloscope controls room for amplitude, frequency, triggering, and also channels. When your teacher has actually helped you obtain a signal using the correct channel and triggering you will use the amplitude and frequency controls to display screen the features of the sound gift produced.

The amplitude mediate of an oscilloscope controls exactly how tall a given voltage will show up on the screen. The purpose of this adjustment is the you have the right to see a very large or a very small signal on the exact same screen.

An oscilloscope


Two different oscilloscope traces


The frequency (or time) convey of an oscilloscope is how much time will certainly a certain distance throughout the display represent. The objective of this mediate is to have the ability to see a very quickly transforming or a slowly transforming signal ~ above the very same screen.

Note:The display screen of the oscilloscope will display you a transverse wave pattern. This does not average that sound waves room transverse waves but just mirrors that the pressure being measure is fluctuating because of a press wave.

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You will have the ability to experiment with different amplitudes and frequencies making use of the duty generator and also see what affect the transforms have on the waveform picked up by the microphone.