Intensity in Decibels and Resonance

Intensity in
Decibels and
Resonance

BY ERICK ROMAN AND GAVITA
RAMAWAD

What is a
decibel?

A decibel is a dimensionless
unit that describes the ratio
of two intensities of sound;
the threshold of hearing is
commonly used as the
reference intensity.

Multiple Choice

The measured intensity of sound depends on both the distance from the source and the ____ of the sound source.

• Volume

• Power

• Frequency

• Energy

Multiple Choice

The perceived loudness of a sound is measured in ____?

• Watts

• Hertz

• Decibels

• Grams

Relative intensity and how its
measured

Relative intensity is the ratio of the strength of a particular sound wave to the
strength of the hearing threshold. Perceived loudness depends logarithmically on
intensity, so using a number equal to 10 times the logarithm of the relative
intensity gives a good measure of human loudness perception. This measure of
loudness is called the decibel level. The decibel level is dimensionless because it is
proportional to the logarithm of the ratio. The values on this scale use a
dimensionless unit called a decibel.

Conversion of Intensity of Decibel

Intensity (W/m^2)

Decibel Level (dB)

EXAMPLES

1.0 x 10^-12

0

Threshold of hearing

1.0 x 10^-11

10

Rustling leaves

1.0 x 10^-10

20

Quiet whispers

1.0 x 10^-9

30

whisper

1.0 x 10^-8

40

Mosquito buzzing

1.0 x 10^-7

50

Normal conversation

1.0 x 10^-6

60

Air conditioner at 6 m

Multiple Choice

When the measured intensity of a sound increases from 1.0 X 10-4 to 1.0 X 10-3 the decibel level increases from 80dB to

• 90dB

• 60dB

• 10dB

• 70dB

Multiple Choice

The decibel level at the threshold of human hearing is ____?

• 100dB

• 1000dB

• 0dB

• 1dB

Multiple Choice

For Fun:

In general, the human ear is most sensitive to sounds having a frequency of about___?

• 1000Hz

• 20Hz

• 900Hz

• 80Hz

Different Vibrations

Force Vibrations – the tendency of an already vibrating object forcing another object
into a vibrational movement through external force like impact.

Sympathetic vibrations/resonance - a chain wave of vibration reacting to one
another in this like harmonic synchronization.

Resonance

Resonance – basically is the effect of a force vibration. You can think of pendulums
hitting one another, with the first pendulum in motion with a vibration hitting the
second pendulum causing a transfer of energy. Which in turn means the amplitude for
the first pendulum will decrease, but the second pendulum's amplitude will increase.
The second pendulum is also mimicking the first pendulums initial vibration.

Multiple Choice

When a string on an acoustic guitar is struck, the hollow body of the guitar vibrates at the same frequency as a result of___?

• Vortex Vibration

• Free Vibration

• Forced Vibration

• Transverse Vibration

Multiple Select

Resonance occurs when a force causes an object to vibrate at____?

• Damped Frequency

• Free Frequency

• Forced Frequency

• Natural Frequency

APA resources

• Physics Textbooks & Digital Programs | Houghton Mifflin Harcourt. (n.d.). Www.hmhco.com. Retrieved April 11, 2023, from https://www.hmhco.com/search?supercategoryid=EDUCATIONPRODUCTS&parentcategorydescription=Science&categorydescription=Physics

• Types of Forces. (n.d.). Www.physicsclassroom.com. https://www.physicsclassroom.com/class/newtlaws/Lesson-2/Types-of-Forces#:~:text=Types%20of%20Forces%20%20%20Type%20of%20Force

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