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SOUND WAVE loudspeaker-waveform …
SOUND WAVE
(ALYAA MAISARAH BINTI MOHMAD ROSMAN)
(FATIN RABBIATULADAWIAH BT SALEHUDDIN)
FUNDAMENTALS OF SOUND WAVES
-Frequency (no. of oscillations in pressure per second).
-Wavelength (distance between each successive region of high or low pressure).
LOUDNESS & PITCH
LOUDNESS
-Depend on the amplitude of the sound wave
-Intensity, I (rate of energy per area)= Watts/m^2 determines loudness
THE SOUND LEVEL
-The human ear can detect an extremely wide range of intensities.
Range(1×10^-12 W/m^2)
-FORMULA :
PITCH
-The frequency of sound wave
-The frequency determines pitch.
-The human ear can detect an extremely wide range of intensities.
-Audible frequency 20Hz-20000Hz,Infrasonic (<20Hz),Ultrasonic (>20000 Hz)
MAXIMUM PRESSURE IN A SOUND WAVE
SUPERSONIC & SHOCK
An object, such as a JET, s said to have supersonic speed if it travels faster than the speed of sound. Such speed defined using "Mach" number.
Stationary Sound Source
(Equally spaced wavelength&Frequency is the same)
Sound source moving at the velocity lower than the speed of sound
(doppler effect takes places wavelength at the front is smaller than in the back)
Speed of source= Speed of sound
(Wave fronts pile up directly in front of the source)
Velocity of sound < Velocity of object
(Wavefronts pile up along the side.The wave crests overlap one another and form a larger amplitude wave known as SHOCK WAVE)
DOPPLER EFFECT
-A change in frequency of a wave that is heard by an observer when there is relative motion between the source of wave and observer.
If SOUND SOURCE moves towards stationary observer (frequency > wavelength)
f’=f [ V sound/ Vsound-Vsource]
If SOUND SOURCE moves away from stationary observer (frequency < wavelength)
f'= f [ Vsound / Vsound+ Vsource)
If OBSERVER moves towards stationary sound source (frequency > wavelength)
f'=f [ Vsound + Vobserver / Vsound ]
If OBSERVER moves away from stationary sound source (frequency < wavelength) f'=f [ Vsound - Vobserver / Vsound ]
COMBINED FORMULA (Useful for when observer & source are both moving)
TRANVERSE AND LONGITUDINAL STANDING WAVE
STRINGED INSTRUMENTS (Many examples of stringed intruments exists (piano,guitar) when the string on the instrument is plucked, it begins to oscillate and produces a STANDING WAVE.
-Formula ( fn=n v / 2L ) (n=1,2,3,4,....)
WIND INSTRUMENTS (These instruments produced sound waves in a column of air within a tube. Some example include the FLUTE & ORGAN PIPE.
-LONGITUDINAL OPEN AT BOTH ENDS (fn=n v/2L)(n=1,2,3.4....)
-LONGITUDINAL OPEN AT ONE END (fn=n v/4L) (N=1,3,5,7...)
DIFFRACTION & SOUND (Bending of sound around a barrier)
CONTRUCTIVE&DESTRUCTIVE INTERFERENCE
SINGLE SLIT DIFFRACTION
CIRCULAR OPENING (1ST MINIMUM)
DOUBLE SLIT DIFFRACTION
BEAT FREQUENCY= No of cycle/Time elapsed
(ALYAA MAISARAH BINTI MOHMAD ROSMAN)