Ch 2 (Sound) Flashcards
Sound
All sounds are produced by the viberation of objects. Sound is a form of energy that travels in the form of waves from one place to another.
Condition for production of sound
The body should viberate
Loudness
Characteristic of sound by which loud and faint sounds can be distinguished
Loudness c
Characteristic of sound by which loud and faint sounds can be distinguished
Eg,
Adressing to friend and adressing to a gathering
Factors affecting loudness
4
Amplitude of viberating body
Area of viberating body
Distance from viberating body
Hearing ability of listener
Relation of loudness with amplitude
Directly proportional
Relation of loudness with area
Directly proportional
Relation of loudness with distance
Inversely propotional
Due to a decrease in amplitude due to an increase in distance
Pitch
The characteristic of sound by which we can distinguish between shrill and grave sound
Pitch depends on? How?
Frequency
Directly proportional
Quality
Characteristic of sound by which we can distinguish two sounds of same pitch and loudness
For example. Notes of piano and a flute
Quality depends on
Waveform
Intensity
Sound energy passing through a unit area held perpendicular to the direction of propogation of sound waves
Unit of intensity
W per m²
Watt per meter square
Dogs can hear frequency?
20,000 to 25,000 Hz
Zero bel
The barely audible and faintest intensity of sound is (10 raised to power minus 12)
Intensity level
The difference between loudness of unknown sound and loudness L⁰ is called intensity level
Decibel scale
A scale used for measuring intensity of sound. It is the lagorithmic measure of amplitude of sound waves. In the logarithmic scale, equal intervals correspond to multiplying by 10 instead of adding equal amounts.
Formula for intensity level
10 log I/I⁰ dB
Intensity in Wm² and dB of jet plane
10 ³ and 150
Intensity in Wm² and dB of siren
10⁰ and 120
Intensity in Wm² and dB of whisper
10-⁹ and 30
Intensity in Wm² and dB rustling if leaves
10-¹¹ and 10
Intensity in Wm² and dB of threshold
10-¹² and 0
Reflection of sound (echo)
Sound travelling in a medium falls on another medium bouces back to the first medium
Blue whale’s rumble (dB)
180 dB
Musical sounds
Sounds pleasant for our ears, eg flute violen etc
Noise
Sounds that produce unpleasant and jarring effects on our ears, eg, slamming of door and sounds of traffic etc
Noise pollution
Level of noise that has bad effect on human health, animals and plants etc eg sound of traffic, heavy machinery
Safe level of noise for humans
85 to 90 dB
Health effects of noise pollution
Aggression,high stress level , hearing loss, sleep disturbances etc
Acoustics
Study of sounds, its effects, properties and production
Acoustic protection
The technique or method used to absorb undesireable sounds by soft and porous surfaces
Reverberations
Sometimes, when the sound is reflected by the walls, ceilings, and floor, the reflecting surfaces are too reflecting, and sound becomes garbled. This is due to multiple reflections called reverberations.
Audible frequency for humans
20 to 20,000 Hz
Audible Frequency range def
The range of frequencies that humans can hear
Ultrasounds def
Sounds of frequency higher than 20,000 Hz which are inaudible to human ear are called ultrasounds or ultrasonic waves
Bats’ audible frequency
Up to 120,000
Mice audible frequency
Up to 100,000
