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+ Perceiving Sound

Perceiving Sound

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Perceiving Sound. Before we start!. A review of Light. Light vs. Sound. What do you think is going to happen? . Make a prediction. What will happen when air is removed from the bell jar? Don’t forget to explain why. . Make Observations. Why did this happen? . Sound is… . - PowerPoint PPT Presentation

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Page 1: Perceiving Sound

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Perceiving Sound

Page 2: Perceiving Sound

+Before we start! A review of Light

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+Light vs. Sound

Light Sound - Transverse waves -Longitudinal waves Electromagnetic waves

- mechanical waves: require a medium to travel.

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+What do you think is going to happen? Make a prediction. What will happen when air is removed from the bell jar?

Don’t forget to explain why.

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+Make Observations

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+Why did this happen?

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+Sound is…

A mechanical wave. Longitudinal wave. Produced by the vibration of an object

and transmitted to the object’s environment.

Requires a medium.

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+The speed of Sound

It changes from one medium to another.

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+Why is that? Using the particle model to justify your

answer. Why does sound travel faster in solids than in gases?

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+The Decibel (Db)

The unit of measurement for the intensity of sound. High Intensity sound = High amplitude = More

Decibels.

Low Intensity sound = Low amplitude = Low Decibels.

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+The Decibel Scale

All decibel measurements are not completely accurate, they are related to our perception by the human ear.

A sound measuring 0 Db is can barely be heard by the ear.

We measure variations on the scale by a factor of 10.

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+A Sample of a Decibel Scale

Another one can be found on p. 103 of your textbook.

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+Try some Questions

P. 118 # 8- 10

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+Pitch and Frequency Lower Pitch = lower frequency sound. High Pitch = Higher frequency sound.

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+Infrasound and Ultrasounds

Infrasounds = sounds under 20Hz Used by some animals to communicate. E.g. Elephants

Ultrasounds = sounds above 20 000 Hz Used in medical imaging Used by some animals like bats (echolocation)

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+Can we hear all frequencies?

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+What happens when you age?

http://www.youtube.com/watch?v=qNf9nzvnd1k

http://www.youtube.com/watch?v=VxcbppCX6Rk