Presentation on theme: " The intensity of a sound is related to the amount of energy flowing in the sound waves. It depends on the amplitude of the vibrations producing the."— Presentation transcript:
The intensity of a sound is related to the amount of energy flowing in the sound waves. It depends on the amplitude of the vibrations producing the waves.
The larger the amplitude of vibration is, the more intense will be the sound.
The loudness of a sound refers to how strong the sound seems to us when it strikes our ears. At a given frequency, the more intense the sound is, the louder it seems.
Water waves in a pond get weaker as they travel away from their source. In the same way, sound waves lose intensity as they spread outward in all direction from their source.
Thus, the loudness of a sound decreases as the distance increases between a person and the source of the sound.
A sound wave that is twice as loud has roughly ten times the intensity.
ß (in dB) = 10 log (I/Io) b – is the loudness measured in decibels (dB) I – is the intensity of the sound wave in watt/m^2 Io – is a constant equal to 1 x 10^-12 watt/m^2
Io represents the most faintly heard sound by humans and is defined as the loudness of 0 dB. Just as for gravity, electricity and magnetism, the intensity of sound drop off as the inverse square of the distance from the source.
Scientist use a unit called decibel to measure the intensity level of a sound. A 3000-hertz tone of zero decibels marks the threshold of audibility- the weakest sound that the normal human ear can hear. A sound intensity level of 140 decibels is the threshold of pain.
Sounds of 140 decibels or more produce pain in the ear, rather than hearing. A whisper amounts to about 20 decibels. Ordinary conversation has an intensity level of about 60ndecibels. Loud rock music can produce up to 120 decibels.
The sound in a particular place has an intensity of 2.0 x 10^-7 W/m^2. what is the loudness of the sound? If the intensity is tripled, what is its corresponding loudness? Note: Io = 1 x 10 ^-12 Watt/m^2 is the threshold audibility of human ear.
Given: Sound intensity I 2.o x 10^-7 W/m^2 Find: a. Loudness (ß) at the current intensity b. Loudness (ß) if the current intensity is tripled.
Solutions: a. Using the equation given. ß (in dB) = 10 log ( I/Io ) = 10 log (2.0 x 10^-7 W/m^2 / 1 x10^-12 W/m^2 = 10 log (2.0 x 10^5) = 10 (5.3) = 53 dB
b. When the current intensity is tripled. Using the same equation given. I = 3 (2.0 x 10^-7 W/m^2) = 6.0 x 10^-7 W/m^2 ß (in dB) = 10 log ( I/Io ) = 10 log (6.0 x 10^-7 W/m^2 / 1 x10^-12 W/m^2 = 10 log (6.0 x 10^5) = 10 (5.8) = 58 dB