Classification and Characteristics of sound as per GTU Syllabus.

1. Classification and Characteristics of
sound
Harsh Parmar
ID: 16BEITG005
Sub: Physics Seminar

2. 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.

3. Classification Of Sound
Infrasound f<50 Hz
Audible Sound 20 Hz To 20kHz
Ultrasound f>50 Hz

4. 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

5. Properties Of Musical Sound
 Regular in Shape.
 Have definite Periodicity.
 They do not undergo a sudden change in
amplitude.

6. Properties Of Noise
 Irregular in Shape.
 Do not have Definite Periodicity.
 They Undergo a Sudden Change In Amplitude.

7. Characteristics Of Musical Sound
Pitch
Related To Frequency Of Sound
Loudness
Related To Intensity Of Sound
Timbre
Related To Quality Of Sound

8. 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.

9. 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 I
Where K Is Constant

10. 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

11. 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

12.  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.

13.  Sabine’s formula works for large enclosures.
However, it leads to paradox for highly absorptive
surfaces. For instance when a = 1, all sound energy
incident on the surface is absorbed and T = 0. Such
room 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 as
Following.
EYRING’S EQUATION:

14. Sabine’s Formula
Sabine’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:

15. Thank You