1.4 Loud and Soft Flashcards
What does the loudness of a sound wave depend on?
The amount of energy that is transferred to the surroundings by the vibration. For example, when a trumpeter blows harder into a trumpet then more work is being done on the air and so there will be more energy in the sound wave.
What is the proportionality of energy, E to amplitude, A?
E is found to be proportional to the square of A. Doubling amplitude increases energy by a factor of four etc.
What does the fact that sound waves spread out in all directions from a point mean?
The total energy that is emitted will be spread increasingly thinly the greater the distance from the source.
How do the sensitive ears of humans pick up sound waves of extremely low frequency such as 1 x 10^-12 Wm ^-2?
By detecting the change in the atmospheric pressure produced by the sound.
What is the faintest sound that a human ear can detect known as?
The threshold of hearing.
How do you find the number of decibels?
Divide the intensity by 1 x 10^-12 Wm squared and express this as a power of 10.
What does the word noise mean?
A variation of sound or an electrical signal that obscures or reduces the clarity of a signal. This variation is often random and persistent.
What three things can be done to reduce the effects of noise?
Reducing it at the source
Absorbing it
Masking it
What is white noise?
Noise containing many frequencies with equal intensities.
Give examples of how noise is reduced everyday.
Vehicle exhausts use bafflers to muffle the noise produced by the engine.
Cubicles in offices are to used to section of noises.
Carpeting on floors has a good sound absorbing effect.
How do active noise cancelling headphones work?
A microphone samples the surrounding noise and electronic circuits generate a sound of similar frequency and amplitude but anti-phase with the original sound. The superposition of the two sounds cancels the original sound.
Difference between loudness and intensity?
Loudness is related to the amplitude of sound waves
intensity is the rate at which power is transferred across a given area
