Ch 3 Sound and Its Measurement

Question 0

Brownian Motion

Answer 0

The rapid and random movement of air particles. Can be affected by the heat in an environment.

Question 1

Elasticity

Answer 1

The springiness of molecules in a medium. The greater distance between molecules, the greater elasticity.

Question 2

Waves

Answer 2

The succession of molecules being shoved together and then pulled apart.

Question 3

Compressions

Answer 3

Where molecules are pushed together, becoming compressed.

Question 4

Rarefactions

Answer 4

When molecules are pulled apart, becoming less dense.

Question 5

Transverse Waves

Answer 5

A wave where the molecular motion is perpendicular to the direction of wave motion.

Question 6

Longitudinal Waves

Answer 6

A type of wave where the molecules move along the same axis as the wave itself when a force is applied.

Question 7

Cycle

Answer 7

The time it takes for one wave, which is one compression and one rarefaction, to go by.

Question 8

Frequency

Answer 8

Cycles per second.

Question 9

Ocsillation

Answer 9

One cycle of vibration, which starts from any part of a wave and goes to the same part of the next wave.

Question 10

Sine Wave (Sinusoidal Wave)

Answer 10

A type of wave that takes one oscillation and uses it for a number of mathematical analyses that are important in the study of acoustics. The wave starts at 0 degrees.

Question 11

Pure Tone

Answer 11

When a body oscillates sinusoidally, showing only one frequency of vibration with no tones superimposed.

Question 12

Cosine Wave

Answer 12

Same as the sine wave, but instead of starting at 0 degrees, it starts at 90 degrees.

Question 13

Free Vibration

Answer 13

Vibration that has no outside fore being added to perpetuate the swinging.

Question 14

Forced Vibration

Answer 14

A vibration that an outside force is added to that controls the vibration, causing it to continue unaltered until the outside force is removed.

Question 15

Period

Answer 15

The amount of time it takes for one cycle to occur.

Question 16

Frequency

Answer 16

Frequency = 1/Period

Measured in Hz

Question 17

Greater mass on an oscillating system

Answer 17

Increase in mass decreases velocity

Question 18

Compliance

Answer 18

Reciprocal of stiffness. As compliance increases, the frequency at which the body is most easily made to vibrate decreases.

Question 19

Resonant Frequency

Answer 19

A natural rate of vibration of a mass, which is the frequency at which it is most easily set into vibration and at which the magnitude of vibration is greatest and decays most slowly.

Question 20

Amplitude

Answer 20

The measurement of a wave from it’s equilibrium point to it’s highest point (crest) or it’s lowest point (trough)

Question 21

Velocity

Answer 21

The speech with which a wave travels from the source to another point.

Question 22

Wavelength

Answer 22

A measurement from any point on a sinusoidal wave to the same point on the next cycle of the wave. The formula for determining wavelength is w=v/f. Can also be shown as v=fw or f=v/w.

Question 23

Phase

Answer 23

When the starting and ending points of cycles from different waves are aligned so that the 0 degree point of each angle is lined up with the other.

Question 24

Cancellation

Answer 24

When two tones have an identical frequency, but are 180 degrees out of phase with each other. When this occurs, the waves cancel each other out.

Question 25

Beats

Answer 25

Changes in amplitude which are perceived by the ear as beats.

Question 26

Complex Wave

Answer 26

A sound that contains a number of different frequencies, amplitudes, and phase relationships.

Question 27

Fourier first showed that any complex wave can be analyzed in terms of its?

Answer 27

Sinusoidal components

Question 28

Harmonics

Answer 28

Tones that occur over a fundamental.

Question 29

Spectrum

Answer 29

A group of harmonics/overtones that starts at the fundamental and increases in frequency in increments of the fundamental. An example is a spectrum with a 100 Hz fundamental. The lowest sound in the harmonic spectrum is 100 Hz, whereas the next is 200 Hz, 300 Hz, etc.

Question 30

Intensity

Answer 30

How far a body of sound travels

Question 31

Dyne (d)

Answer 31

A unit for measuring small changes in the force of a sound.

Question 32

Pressure

Answer 32

A force generated over a surface area

Question 33

Work

Answer 33

When any mass, such as a group of air particles, is moved

Question 34

Power

Answer 34

The capacity to exert physical force or energy

Question 35

Intensity

Answer 35

Intensity (watts/cm^2) = power (watts) / 4pie x radius^2 (cm)

Question 36

Decibel

Answer 36

A unit of measuring sound intensity. Decibels cannot be simply added or subtracted because they are logarithmic.

Question 37

Intensity Level Equation

Answer 37

dB(IL) = 10 x log(Io/Ir)

Question 38

Sound Pressure Level Equation

Answer 38

dB(SPL) = 10 x log(Po^2/Pr^2)

Question 39

Sound-level meters

Answer 39

A device designated to measure the sound-pressure levels in various acoustical environments.

Question 40

Hearing Level (HL)

Answer 40

The lowest sound intensity that stimulates normal hearing is called zero hearing level.

Question 41

Threshold

Answer 41

The threshold of a pure tone is usually defined as the level at which the tone is so soft that it can be perceived only 50% of the time it is presented.

Question 42

Sensation Level (SL)

Answer 42

The number of decibels of a sound above the threshold of a given individual.