Physical Semestral Guide 2/many

​Types of sound

There are many different types of sound including, audible, inaudible, unpleasant, pleasant, soft, loud, noise and music.

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1.      Sound waves are

waves that cause to compress and expand in the direction that the wave is moving.

​Infrasonic Waves (Infrasound)

Infrasonic waves have frequencies below 20 Hz, which makes them inaudible to the human ear. Scientists use infrasound to detect earthquakes and volcanic eruptions, to map rock and petroleum formations underground, and to study activity in the human heart.

​Ultrasonic Waves (Ultrasound)

Sound waves that have frequencies higher than 20,000 Hz produce ultrasound. Because ultrasound occurs at frequencies outside the human hearing range, it is inaudible to the human ear. Ultrasound is most often used by medical specialists who use sonograms to examine their patients’ internal organs.

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wave: Is a wave in which the motion of the medium’s particles is parallel to the direction of the energy transport. Sound waves in air and fluids are this type of waves because the particles that transport the sound vibrate parallel to the direction of the sound wave’s travel.

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wave: Is a wave that depends on the oscillation of matter, meaning that it transfers energy through a medium to propagate. These waves require an initial energy input that then travels through the medium until the initial energy is effectively transferred.

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Wave

: Is the number of waves per second.

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: Is essentially the number of seconds per wave

​Relation between frequency and period

f = Frequency

T = Period 

​The frequency is measured in Hertz (Hz), the Wavelength is measured in meters (m) and Period is measured in seconds (s).

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_______ ______:Describes the changes (increase or decrease) in the frequency of any sound or light wave produced by a moving source with respect to an observer.

If the relative velocity of observer and source are towards each other the frequency will be higher than the original frequency.  If the relative velocity of observer and source are away from each other the frequency will be lower than the original frequency.

Doppler Effect

Doppler Effect of Sound Equation

​Where:

f = frequency perceived

f_o = original frequency from the source

v = velocity of sound

v_o = velocity of the observer (+ if going towards the source and - if going away from the source)

v_s = velocity of the source (- if going towards the source and + if going away from the source)