perceiving sound
DESCRIPTION
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 PresentationTRANSCRIPT
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Perceiving Sound
+Before we start! A review of Light
+Light vs. Sound
Light Sound - Transverse waves -Longitudinal waves Electromagnetic waves
- mechanical waves: require a medium to travel.
+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…
A mechanical wave. Longitudinal wave. Produced by the vibration of an object
and transmitted to the object’s environment.
Requires a medium.
+The speed of Sound
It changes from one medium to another.
+Why is that? Using the particle model to justify your
answer. Why does sound travel faster in solids than in gases?
+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.
+A Sample of a Decibel Scale
Another one can be found on p. 103 of your textbook.
+Try some Questions
P. 118 # 8- 10
+Pitch and Frequency Lower Pitch = lower frequency sound. High Pitch = Higher frequency sound.
+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)
+Can we hear all frequencies?
+What happens when you age?
http://www.youtube.com/watch?v=qNf9nzvnd1k
http://www.youtube.com/watch?v=VxcbppCX6Rk