Hearing exam 1

A vibratory energy transmitted by pressure waves through a media (like air)

The perception of sound

What and where and pitch

location

Location

*Location

How the vibrations change over time

The rate, or frequency, of vibrations (how often it repeats)

The magnitude, or amplitude, of a vibration (how much energy is in the signal)

Seconds (s)

Milliseconds (ms)

Microseconds (µsec)

Hertz (Hz)

Kilohertz (kHz)

Megahertz (MHz)

Gigahertz (GHz)

DB (db) decibels

Mass, TIme, length

• Has magnitude

• Ex) mass, time, & length

• Has magnitude AND direction

• Ex) displacement, velocity, acceleration, force, work, energy, momentum, power, intensity, pressure

Has the potential for work. Is something a body posses

Potential, kinetic and total

Rate at which work is accomplished

OR

Rate at which energy is expended, transformed, or transferred

Mass and elasticity

A mechanical disturbance that is propagated through an elastic medium

Simple Harmonic Motion: an object moving in a harmonic motion, then changes in displacement, velocity & acceleration, creating a sinusoidal motion

A displacement of the medium where a wave travels that is PERPENDICULAR to the direction of the wave propagation

Particle displacement is PARALLEL to the wave of propagation.

Longitudinal pressure waves

Compression of a medium

Expansion of the medium

How we represent change of a physical quantity as a function of time.

Indicates a certain stage in the cycle of motion by using angles from the UNIT CIRCLE

The displacement or location in the wave (in degrees) at the point where the vibration begins and time is 0

Same frequency & same phase

Same frequency & different phase

Positive Shift

Reaches peak amplitude first

Negative Shift

Reaches peak amplitude last

The magnitude of a waveform at any given moment of time

The rms value is obtained by squaring the amplitude of each point of a waveform and then averaging those points. For complex sounds, we can use a sound level meter to calculate the rms

Wavelength depends upon the medium in which it is traveling. This is in contrast with frequency which is a constant.

Higher frequencies have shorter wavelengths

1. Sinusoid/sine wave

2. Uniform circular motion

A uniform circular motion describes SHM when a body moves around the circumference of a circle at a constant rate

When a sound source vibrates the molecules in the air, the molecules show NO NET MOVEMENT, but they vibrate with the motion of the sound source

Intensity decreases proportionately to the square of the distance from the sound source

There is a rapid drop in sound intensity with increasing distance

the total opposition to motion

*this changes the sound wave*

will determine whether the sound wave gets REFLECTED, TRANSMITTED, or  ABSORBED by the media

Bounces off

Passes through

absorbed by new medium

Results in INCREASED displacement, as the waves  add together

Results in REDUCED displacement, as the waves cancel out

1. The size of the object that the sound wave is encountering

2. The wavelength of the sound wave

Amplitude as a function of time (a waveform)

Fourier Series

Describes frequency, amplitude, and starting phase

1. Amplitude spectrum

2. Phase spectrum

Ways we can break down complex vibrations into simple sinusoidal vibrations

Breaking down sounds into their parts

Recovery of amplitude and phase spectra from waveform

Putting sounds together to make complex sounds

Add instantaneous amplitudes of waveform

NOT a sinusoidal waveform

Can be defined by a line spectrum AND/OR continuous spectrum

Can be PERIODIC or APERIODIC

Repetitive pattern

Line spectrum

No repetitive pattern

Continuous spectrum

The first harmonic

integer multiples of the fundamental frequency

A transient stimuli– a sound that has an abrupt, quick “on” and “off”. They have a rapid onset and very short duration.

Broad continuous spectrum

power in a large band of frequencies

Power in a limited band of frequencies

Am and Fm

Mechanism by which frequencies are selectively passed or rejected

The cochlea acts as a filter to analyze the frequencies of complex sounds, such as speech.

The frequency where the filter begins to attenuate the input signal. There can be a lower and upper cutoff frequency.

The frequency midway between the upper and lower cutoff frequencies (for band-pass and band-reject filters)

Range of Frequencies

The amount of attenuation

We measure this in dB per octave change in frequency

Doubling or “halfing” of a frequency

A signals spectrum and time domain waveform