Sound

• How are sounds Classified?

• How are sounds produced?

• How are sounds different?

• How are sounds measured?

• How fast does sound move?

Sound Waves• Each Sound wave

has unique pattern

• Frequency

• Wavelength

• Amplitude

Sound mediums

• A medium is a material that sound, a form of energy, need to transfer

• Speed of sound– Solid : Fast speed– Liquid : Medium speed– Gas : Slow Speed

• Standard Temperature and Pressure = 3.31 x 102 m/s

– Vacuum : No Sound

Frequency of Sound

• Pitch of the sound• Musical notes: there are 12 notes on a staff from

A to G#• Bass : Low frequency 0 to 300 Hz• Mid range : “voice” 300 to 6,000 Hz• Treble : High frequency, Above “middle” C

note, 6,000 to 20,000 Hz• Spectrum of frequency

Amplitude of Sound• Volume control• Loudness• Strength of the wave ( measured in db “decibels”)• Energy of the wave

Reflection and Refractions of Sound waves

• Echo – Reflection of sound off a surface (Acoustics (Greek

akouein,”to hear”),. It is more commonly used for the special branch of that PHYSICS that deals with the construction of enclosed areas so as to enhance the hearing of speech or music.

• Reverb (Electronic echo)• Resonance

– electronic envelope Helmholtz Resonator, spherical vessel of metal or glass with an opening and an earpiece on opposite sides.

– The ear canal acts enhancing frequencies in the range from 1000 to 4000 Hz (hertz, or cycles per second).

Speed of Sound• Velocity(v) of a wave= Frequency (f) times the

wavelength (• V = f • The speed of propagation of sound in dry

air at a temperature of 0° C (32° F) is 331.6 m/sec (1088 ft/sec). If the temperature is increased, the speed of sound increases; thus, at 20° C (68° F), the velocity of sound is 344 m/sec (1129 ft/sec)

Resonance of Sound• Any oscillating object has a natural

frequency, which is the frequency an oscillating object tends to settle into if it is not disturbed.

•The phenomenon in which a relatively small, repeatedly applied force causes the amplitude of an oscillating system to become very large is called resonance

Interference of Sound• Constructive interference

–The displacement of the disturbance of 2 waves are the same (Similar sounds•Frequency are the same or multiple.

•Destructive interference–The displacement of the disturbance of 2 waves are the different (Unlike sounds)

•Frequency are the different or not a direct multiple.

Beats• The pulse, or pattern of regular accents, of a musical piece can be broken into individual pulses, or beats

• a fractional symbol in which the numerator specifies the number of beats per bar, and the denominator specifies the relative note value assigned to one beat

Doppler Effect• The frequency of the perceived wave is

changed by the motion of the source

– Increasing Frequency when the source approaches the sensor

– Decreasing Frequency when the source increases the distance from the sensor

Summary

• Sounds are created by Moving molecule in the medium ( Solid, Liquid and Gases)

• Sounds are measured by Frequency, Wavelength, Speed, and Amplitude.

• Sounds can combine by interference• Sounds can be changed by the Acoustics of the

Area or the speed of the source (Doppler Effect)• Sounds are used in many devices.