Sound

CSD 230

Soundwave

A disturbance created in a medium, such as air, by a source of vibration

Waveform

A graphical description of the variation in a sound wave’s amplitude as a function of time

Decibel

The unit of measure used to describe the level or magnitude of a sound wave

air particles

The presence of ________ makes the production of a sound wave possible.

elasticity

Once the applied force is removed, a property of the air medium, known as its __________, returns the displaced particle to its resting state.

F; in the direction

T/F: When sufficient force is applied to air particles by a moving object, the air particles will be moved or displaced in the opposite direction of the applied force.

Vibration

Consists of movement or displacement in more than one direction

simple harmonic motion

The most fundamental form of vibration is...

a simple mass attached to an elastic spring

Another common physical system that is used to represent simple harmonic or sinusoidal motion is…

Free vibration

an object is allowed to vibrate encounters opposition (friction). If no outside force is added to perpetuate the movement then that is called ________.

Friction

_______will cause an object to slow down until all swinging stops

Sinusoidal

Free vibration is always ________ and the frequency always stays the same.

sine; sinusoidal

Displacement and time are related to each other by the _______ function. Therefore, simple harmonic motion is often referred to as______ motion.

sinusoidal motion

Simple harmonic motion is often referred to as_______

cycles per second (cps)

Sinusoidal motion is measured in how many cycles are completed in one second or …

Hertz (Hz)

In audiology cps is measured in ______

Pure tone

When a wave oscillates sinusoidally showing only one frequency of vibration with no tones superimposed

amplitude, frequency, phase

All vibration, including sinusoidal vibration, can be described in terms of its…

Amplitude; louder

______ is the pressure wave. A sound of higher amplitude is perceived as being ________ than a sound of lower amplitude.

resonant frequency

The natural rate of vibration of an object

period

1 cycle of vibration (seconds per cycle); The time it takes for the pendulum to move from any point and return to the same point

frequency

# of cycles of vibration completed in 1 sec (cycles per sec)

Phase

The starting position of the mass or the _____ relationship between two vibrating pendulums or mass. If they start at opposing poles- then they will negate themselves, result in cancellation of the sound (180 degrees difference)

zero

Two tones of identical frequency but 180 degrees out of phase cancel other resulting in _____ amplitude. –RARE!

F; increasing

T/F: Two tones of the same frequency and phase relationship reinforce each other, decreasing the amplitude.

Wavelength of the sound wave

The distance between two successive condensations or high-pressure areas of vibrating air

F; small

T/F: If the frequency of vibration is high, the separation between successive high-pressure areas is large.

pitch, wavelength

2 primary types of resonance that impact the speech signal. Taken together, these resonances shape the sound generated by the individual speaker.

pitch

The mass and stiffness of the vocal cords determines the ________ of the speaker’s voice

wavelength

The __________ resonance that is determined by the length and shape of the vocal tract.

pressure

the parameter most often used to describe sound waves because most measuring devices, such as microphones, respond to changes in sound pressure, and the ear, beginning at the eardrum, responds to changes in _______.

Pascal (Pa)

The unit of sound pressure is

sound field

A region containing sound waves

free field

A sound field without reflected sound waves

diffuse field

A sound field where sound is reflected from many surfaces

T - distributed equally

T/F: Sound pressure is distributed equally throughout the measurement area in a diffuse field.

Interference

Results when multiple sound waves encounter one another

Constructive interference

The 2 sound waves add together to yield a sound wave that is greater in amplitude than either wave alone.

Destructive (neg) interference

The amplitude of the sound wave resulting from the interaction is less than the amplitude of either wave alone.

Sound shadow

When sound encounters an object

Sound diffraction

When a sound wave changes direction

Sound reflection

This is determined by the impedance of the medium

increases

Sound pressure decreases in amplitude as the distance it travels ______ (increases or decreases).

the inverse square law

Every doubling of the distance from the sound source in a free field situation, the sound intensity will diminish by 6 dB

resonant frequency!

The frequency at which the system vibrates maximally for equal applied force

Impedance

The net opposition to vibration resulting from the mass, elasticity, and resistance of the system.

admittance

The reciprocal of impedance and indicates how easily energy is “admitted” through a system, rather than “impeded” by it

decreases

As impedance increases, admittance _______ (decreases or increases)

True

T/F: Impedance summarizes the overall opposition to vibration , whereas admittance reflects the ease with which the system is set into vibration.

mass

The greater the _______ (M) of an object, the greater the opposition to movement or vibration (Xm).

vibration

The greater the impedance, the lesser the amount of ______ or movement.

Fundamental frequency

When a number of pure tones are presented one of them will naturally have a frequency lower than the others

first harmonic (fundamental frequency)

The component of a periodic soundwave having the lowest frequency is known as the

pitch!

The fundamental frequency is the primary determinant of the ____________ of a speaker’s voice.

T

T/F: Although a fundamental frequency determines all the harmonic frequencies the harmonics do not all have the same amplitude

formants

Peaks in audio are called

Octave

Means a doubling of the frequency.

250 Hz

In audiology we test at each octave starting at _____Hz.

250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz and 8000 Hz

Frequencies tested in audiology

20 micropascals

Lowest sound pressure that can be heard by average young adults

140 dB

Max tolerable sound pressure

0 dB

Just audible sound pressure

Pressure (Pascals) detectors

Most measuring devices for sound are …