W7 Activity 2 - Intensity and Loudness

W7 Activity 2

Intensity and Loudness

By Nicholas Carrillo

​When a guitar string, or drum membrane vibrates back and forth, they compress and expand (rarefaction) the air around them.

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Image Source

Compression and expansion creates pressure waves that are the sound​ waves we hear and feel.

​The guitar strings vibrate the air.

Multiple Select

What kind of waves do you see in the video?

(Select all that apply)

• Standing Waves

• Transverse Waves

• Longitudinal (Compression) Waves

• Continuous Waves

The amount of energy a wave carries is proportional to the square of its amplitude.

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Energy α (Amplitude)²

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​∝

Intensity of a sound wave is its power divided over the area it covers.

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​Intensity = Power/Area

As sound waves spread out, the intensity decreases.

Multiple Choice

As a sound wave spreads out, its intensity...

• Decreases

• Increases

• Stays the same

Multiple Choice

The Energy of a sound wave is proportional too...

• ...the square of its amplitude (A²)

• ...just is amplitude (A)

• ...the speed of the sound wave

• ...the wavelength of the sound wave

The loudness of a sound wave is related to its intensity.

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As the intensity drops, sounds become quieter.

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Subject | Subject

Sound Loudness is measured in decibles (dB)

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For every 10 decibel difference, the loudness changes by a factor of 10​

Example: How much louder is a 70 dB sound compared to a 30 dB sound?​

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70dB - 30dB = 40dB

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For every 10dB difference; change by factor of 10. 40/10 = 4

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10*10*10*10 = 10⁴​ = 10,000x louder!

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Multiple Choice

How much louder is a 50dB sound than a 30dB sound?

• 10x louder

• 100x louder

• 1000x louder

• 10,000x louder

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The range of sounds humans can hear is quite larger!