Pitch, Loudness, andQuality of Sound

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Frequency and PitchPitch = frequency of sound

The perceived pitch of a sound is just the ear's response to frequency.

A high pitch (>2kHz) will be perceived to be getting higher if its loudness is increased, whereas a low pitch (<2kHz) will be perceived to be going lower with increased loudness.

A high pitch sound corresponds to a high frequency sound wave and a low pitch sound corresponds to a low frequency sound wave.

The ear has an ability to detect such frequencies and associate them with the pitch of the sound, because sound waves traveling through air are longitudinal waves which produce high- and low-pressure disturbances of the particles of the air at a given frequency.

timepres

sure

period

Low frequency wave

timepres

sure

High frequency wave

period

The pitch of a note increases with the frequency of vibrations

Intensity and Loudness

The intensity of a sound wave depends on the amount of energy in each wave.

Intensity of a sound wave increases as its amplitude increases.

Loudness is the human perception of sound intensity.

The higher the intensity and amplitude, the louder the sound .

The loudness of a sound increases with the amplitude of vibration .

The intensity of a sound is measured in units called decibels (dB) .

The faintest sound that can be heard by most human ear is 0 dB. Sound with intensities above 120 dB may cause pain and hearing loss .

Familiar sounds and their intensity

Disturbing

The noise levels of common soundsNote that the prolonged listening to loud

music through headphones/earphones can damage your ears as well

Unbearable140Nearby jet at take off

Ear uncomfortable120Police car sirine

Ear pain130Music concert

Working efficiency falls100Shouting in ear

Conversation impossible110Heavy hammering machine

Ear damage> 150

Signs of ear damage; ringing in ears90Pneumatic drill

Annoying if not involve80Motorcycles and cars

60School dining hall

Normal conversation possible50Hair dryer

Soothing30Soft whisper

Limit of hearing0Pin dropping

EffectLevel (dB)Noise

The amount of energy which is transported through a given area of the medium per unit of time is known as the intensity of the sound wave.

Intensity Calculation

Intensity =Energy

Time x Area=

Power

Area

Typical units for expressing the intensity of a sound wave are Watts x meter -2 ( W m ∙ -2 ).

The pitch of the notes produced by stringed instruments depends on :1. the tension2. the length; and3. the mass per unit length (or thickness)

To obtain a note of higher pitch, the frequency of the string can be increased in the following ways :1. increasing the tension2. shortening the length; and3. using the thinner string of smaller mass per unit length

String instruments :

0 dB = a sound which will displace particles of air by one-billionth of a centimeter

0 dB = 1 x 1012 W m∙ -2

Humans are equipped with very sensitive ears capable of detecting sound waves of extremely low intensity = 0 dB

This faintest sound which a human ear can detect is known as the threshold of hearing ( TOH )

To be continued . . . !thank you for watching

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