d. crowley, 2008. pitch & volume to know how the pitch and the volume of a sound affect the...

D. Crowley, 2008

Pitch & VolumeTo know how the pitch and the volume of a sound

affect the sound wave it produces

Speed Of Sound In which medium will sound travel fastest (air; water; brick or

iron)?

Why do you think sound travels faster in some mediums, and slower in others?

Speed Of SoundSound waves disperse less energy when moving through a

medium of greater density

In other words, the denser the medium the faster the sound passes through it (generally)

Sound travels through the iron much more quickly than through air, as the iron is so much more dense (particles are much closer together)

Viewing SoundSound can be studies using a signal generator to produce

different types of sound, a loudspeaker so we can hear the sound, and a oscilloscope which lets us ‘see’ the sound

Signal generator (produces different sounds)

Loudspeaker (allows us to

hear the sound)

Oscilloscope (turns the

sound into a visual signal)

Sound WavesListen to the different sounds produced as the frequency

changes – listen carefully to where your hearing begins / ends

As you listen, view the oscilloscope to see how the waves are changing

AmplitudeA sound can be quiet or loud

Amplitude is a measure of how loud a sound is (how much energy the wave carries) – a big amplitude means a loud sound

A quiet sound on an oscilloscope (short wave

height)

A loud sound on an oscilloscope (tall wave

height)

AmplitudeWhich trace represents the greatest amplitude (loudest sound)?

Sound A has the largest amplitude (tallest waves)so is the louder of the two sounds

A B

Pitch & WavelengthA sound can be low (mooing cow) or high (squeaking mouse)

Pitch depends on the frequency of the waves (number of complete vibrations each second, measured in hertz (Hz))

A low pitch sound on an oscilloscope (few wave per

second)* long wavelength

A high pitch sound on an oscilloscope (many waves per

second)* short wavelength

Pitch & Wavelength Which trace represents the highest pitch, like that of a squeaking

mouse (shortest wavelength)?

Sound B has the most waves across it (short wavelength for each wave) meaning it has a higher frequency = higher

pitch

BA

Wave Variations

Wave EnvelopesSounds can vary greatly in their amplitude (loudness) and

frequency (pitch)

Listen and visualise the sounds and their wave envelopes