Intensity in Decibels and Resonance

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.

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

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.

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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