Classification and Characteristics of sound
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Classification and Characteristics of
sound
Harsh ParmarID: 16BEITG005
Sub: Physics Seminar
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What Is Sound ??
Sound is a Vibration In an Elastic Medium With
definite Frequency & Intensity…
Longitudinal wave .
requires a medium .
cannot travel in a vacuum.
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Classification Of Sound
Infrasound f<50 Hz
Audible Sound 20 Hz To 20kHz
Ultrasound f>50 Hz
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Classification of Audible Sound
• The Sound Which Produces Pleasing Effect On The ear is Called Musical Sound.
• Sounds Of Sitar, Violin, Flute
Musical
• The sound That Produces a jarring effect on the ear and unpleasant to hear is called noise.
• Sound Of Road Traffic, Crackers ,Aeroplan
Noise
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Properties Of Musical Sound
Regular in Shape.
Have definite Periodicity.
They do not undergo a sudden change in amplitude.
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Properties Of Noise
Irregular in Shape.
Do not have Definite Periodicity.
They Undergo a Sudden Change In Amplitude.
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Characteristics Of Musical Sound
PitchRelated To Frequency Of Sound
LoudnessRelated To Intensity Of Sound
TimbreRelated To Quality Of Sound
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Pitch
We can describe pitch by frequency. Rapid vibrations of the sound source(high frequency)produce sound of a high pitch.
Slow vibrations (low frequency) produce a low pitch.
Different musical notes are obtained by changing the frequency of the vibrating sound source.
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Loudness
Loudness is Characteristics which is Common to all sound
■ Loudness & Intensity are Releted to each other by relation
L log I
L = K log IWhere K Is Constant
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Timbre
Quality Of Sound Which Enables us to distinguish between two sounds having the same loudness & Pitch.
Depends on the Presence of overtones.
■ It helps Us To Distinguish musical notes emitted by different musical instruments & Voices Of different Person Even Though the Sound have Same
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A sound produced in a volume is reflected multiple times from the various surfaces. As a result sound persists in the volume for sometime of gradually decreasing intensity even the source stop emitting the sound. This persistence of the sound in a room due to multiple reflections, even when the source stops, is known as reverberation.
Reverberation
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Reverberation time: It is defined as the time during which the sound energy falls from its steady state value to 10-6 times after the source is cut off.
Coefficient of absorption: It is a ratio of sound energy absorbed by its surface to that of total sound energy incident on the surface.
Sabine or Open Window Unit (OWU): 1 m2 Sabine is the amount of sound absorbed by one square meter area of fully open window.
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Sabine’s formula works for large enclosures.However, it leads to paradox for highly absorptivesurfaces. For instance when a = 1, all sound energy
incident on the surface is absorbed and T = 0. Suchroom is called dead room in acoustical terms.
Sabine’s formula does not leads to T = 0 when a =1. Actually, experiments shows that Sabine’s
formula is valid only for a 7 0.2.
Eyeing proposed modification in the equation asFollowing.
EYRING’S EQUATION:
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Sabine’s FormulaSabine’s formula is given by the following:
RT60 is the reverberation time (to drop 60 dB)V is the volume of the room
c20 is the speed of sound at 20°C (room temperature)Sa is the total absorption in sabins
The sabin unit has the same dimension as area (e.g. m2). A one square meter surface with an absorption coefficient of 0.75 would be considered 0.75 sabins. The absorption coefficient has a
range of 0 to 1, where a coefficient of 0 indicates none of the sound is absorbed, and a coefficient of 1 indicates that 100% of it is absorbed.
Since we know the speed of sound at 20°C is 343 m/s, we can do a little math and reduce the formula to:
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Thank You