Sound and Acoustics

Velocity of Sound

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Velocity of sound is determined by measurement of the time delay of pressure pulse detected by a microphone and its distance from the loudspeaker.

Sound Cancellation

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Feed the same signal to two speakers and reverse the connections to one of them. Result: sound cancellation!

Double Sound Source Interference

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Young's experiment performed with coherent sound waves from two loudspeakers.

[In-Depth Description]

Refraction of Sound

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Balloons filled with helium, CO2, or SF6 act as diverging and converging lenses, respectively.

[In-Depth Description]

Sound Reflections in Pipes

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A pulse of sound gets "inverted" when reflecting off the open end of a pipe, but does not get inverted when reflecting off the closed end.

[In-Depth Description]

Inverse Square Intensity

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Sound pressure level of a fire bell decreases by 6dB when distance is doubled.

[In-Depth Description]

Acoustic Horn

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A multicellular horn is shown to amplify sound by 18 dB.

[In-Depth Description]

No Sound Through a Vacuum

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A bell, ringing in a bell jar, ceases to be heard as the bell jar is evacuated.

[In-Depth Description]

Doppler Ball

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Plastic Wiffle Ball with built-in shriek to throw past (or at) your audience.

[In-Depth Description]

Doppler Turntable

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Two speakers, one at each end of rotating platform; beating due to frequency shift of speakers travelling in opposite directions.

[In-Depth Description]

Doppler Whirler

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A high-pitched alarm on the end of a rope is whirled about the head.

[In-Depth Description]

Doppler Tuning Forks

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Run towards the blackboard carrying a tuning fork...

[In-Depth Description]

Sound Waves in a Room

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Three dimensional standing waves are generated in the lecture hall and detected by students moving about.

Helium and Sulfur Hexafluoride

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Change pitch of organ pipes by changing sound velocity.

[In-Depth Description]

Baffle

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Placing a baffle behind a tuning fork (or small louspeaker) dramatically increases the intensity of the sound.

Contact Us

Mailing Address: Lecture Demonstration Services, Science Center, Rm B-08A, 1 Oxford Street, Cambridge, MA 02138
Campus Location: Science Center B-08A | Tel: (617) 495-5824 | Email: scidemos-at-fas.harvard.edu