Vibration of sound- waves

Different waves are different lengths

Sound is made of waves that our ears perceive

Speed of Sound

The speed of sound is different depending on the type of fluid that is being observed. It is based off of how fast a disturbance can travel through a fluid due to the relationship between pressure and density. Refer to equation 1.

Speed of Sound Equation(1)

c = Speed of Sound

dP = Pressure Differential

dρ = Density Differential


Since there is a relationship between pressure and density a pressure wave builds up has an object approaches the speed of sound. Because of this pressure wave, it is impossible for an object to travel exactly at the speed of sound. The reason why is because as the object flies at the speed of sound the pressure wave will continue to build until it destroys the object. This is why jets have after burners. The after burners are used to get the jet past this building pressure wave and essentially break the sound barrier causing the plane to out run its pressure wave which is referred to as the sonic boom. To relate an objects speed to the speed of sound, the Mach number would be used, which is a unit less number. Refer to equation 2.

Mach Number Equation(2)

v = Velocity


Finally, the ideal gas law can also be used to calculate the speed of sound. It will be assumed that an isentropic process will occur. Refer to equation 3.

Speed of Sound and ideal gas law Equation(3)

k = Specific Heat Ratio

R = Ideal Gas Constant

T = Temperature

Vibrations in water

Ticking of a Clock

Try this at home!

Sound Experiment

Lets talk about the ear


Outer ear- What you see of your ear. Ear Canal has little hair on the inside. When you damage your hearing you break the these little hairs and they don’t grow back.

Sound is measured in Decibels (Db)

At what decibel do you start to lose you hearing? With extended exposure, 85 decibels of sound will cause loss of hearing. Extended exposure is about 10 minutes

Normal conversation is at about 59-65 decibels

Sound Levels of Music

Normal piano practice

60 -70dB

Fortissimo Singer, 3′


Chamber music, small auditorium

75 – 85dB

Piano Fortissimo

84 – 103dB


82 – 92dB


85 -111dB




92 -103dB


90 -106dB


85 – 114dB

French horn

90 – 106dB


85 – 114dB

Tympani & bass drum


Walkman on 5/10


Symphonic music peak

120 – 137dB

Amplifier, rock, 4-6′


Rock music peak 150dB


How can you protect your hearing?

How instruments are made:

How A Flute is Made

How a Trombone is Made




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