This document discusses the key characteristics of sound and how it is measured. It defines frequency, time period, intensity, wavelength, sound power, sound pressure, sound pressure level, amplitude, and decibel. Frequency is the number of vibrations per second, measured in Hertz. Intensity is the amount of sound energy received per unit area and time, measured in watts per square meter. Sound pressure level converts sound pressure to the decibel scale. Common tools for measuring sound include measuring intensity in decibels using a reference intensity of 10^-12 watts per square meter. The document also briefly discusses the permissible ambient noise levels defined for different zones in India.

1. Civil Engineering Department
Subject : Environmental
Engineering
Topic : Characteristics of sound and its
measurements
Name : Zala surpalsinh. I
Enroll No : 150600106063

2. Characteristics of sound
• 1.Frequency (f) :
• Number of vibrations (cycles) made in one
second is called frequency of sound.
• Unit of frequency is Hertz.
• 1 Hz = 1 cycle per second.
• The sound of human speech is in the range of
300 Hz to 3000 Hz.

3. • 2. Time period (T) :
• The time taken by the vibrating particle to
complete one vibration ( forth and back ) is called
time period.
• It is the time period between successive peaks or
troughs of the oscillations.
• T = 1/f

4. • 3. Intensity ( I ) :
• Amount of sound energy received per second
from the source of sound per unit area
perpendicular to the direction of wave is called
intensity of sound.
• I = W/A = sound power / unit area perpendicularr
• unit is watt/m² .

5. • 4. Wavelength : The distance travelled by the
sound wave during one time period is known as
wavelength.
• It is the distance between two adjacent crests or
troughs of pressure.
• 5. Sound power :
• it is the sound energy transferred per second
from the source to the air.

6. • 6. Sound pressure :
• It is the amount of air pressure fluctuation
created by the source.
• we hear sound pressure as ‘ loudness '.
• Sound pressure is expressed in pascals (Pa).
• 1 Pa = 1 N/m² (in SI unit)
• in absolute system, unit of sound pressure is
dynes/cm².
• A healthy young person can hear sound
pressures as low as 2*10^-5 Pa.

7. 7. Sound pressure level (SPL ) :
Sound pressure converted in to the decibel scale is
called sound pressure level.
SPL = 20 log10 (p/p0) decibel
Where, p = pressure variation measured in N/m²
p0 = standard reference pressure
= 2*10^-5 Pa

8. • 8. Amplitude of wave (A) :
• The amplitude of wave is the height of the peak
or depth of the trough measured from zero
pressure line.

9. Measurement of sound
The amount of sound energy received per second
from the source of sound, per unit area perpendicular
to the direction of wave is called intensity of sound.
The intensity of sound is expressed in watt/m².
The value of reference intensity is 10^-12 watt/m².

10. • decibel (dB) = 10 log10 (I/Io)
• where, I = measured intensity
• Io = reference intensity = 10^-12 W/m².
• not only, loudness is determines the harmfullness of the
sound but the frequency and pitch of sound is also
responsible for this.
• if a person hears two sounds of same sound pressure but
different frequencies, one sound may appear louder than
the other. This happens because we hear high frequency
noise much better than low frequency noise.
• To take the pitch or frequency of sound in to the account,
a modified scale is used now a days that is decibel-A,
expressed as dBA.

11. Permissible ambient noise
levels in india
Zone
AZoneA

12. Thank you