Hearing Science with quizzes

Oscillation

Regular fluctuation in value, position, or state about a mean value

Sine wave

A simple periodic wave with one frequency component

Simple sound

A sound with one frequency component

Complex sound

A sound with more than one frequency component

Periodic sound

A sound with a repeating waveform pattern

Aperiodic sound

A sound without a repeating pattern

Continuous sound

A sound that continues over time

Transient sound

A brief sound of finite duration

Amplitude

Magnitude of a wave's pressure change

Peak-to-peak amplitude

Measurement from the positive peak of a wave to the negative peak

Baseline-to-peak amplitude

Measurement from the reference line to one peak

Frequency

Number of cycles per second

Hertz

Unit used to measure frequency

Period

Time required to complete one cycle

Frequency-period relationship

Frequency and period are inverses, so f = 1/T and T = 1/f

Wavelength

Distance from one peak or trough of a wave to the next adjacent peak or trough

Wavelength-frequency relationship

If wave speed stays constant, increasing frequency decreases wavelength

Phase

Position of a wave within its cycle, usually measured in degrees

Sound

A vibration that spreads as an audible pressure wave through a medium

Compression wave

The way sound is transmitted through air

Noise

Random unwanted sound that generally carries no useful information

Physical attribute

A measurable property of sound such as amplitude, frequency, or complexity

Psychological correlate

The perceptual experience associated with a physical sound property

Amplitude corresponds to

Loudness

Frequency corresponds to

Pitch

Complexity corresponds to

Timbre

a unit of subjective loudness

Sone

Pitch unit in slides

Mel

Acoustic power

Energy per second

Watt

Unit of power

Sound intensity

Amount of sound energy transmitted per second over a unit area

Intensity unit in MKS

Watt per square meter

Intensity unit in CGS

Watt per square centimeter

Absolute intensity

Actual intensity value in physical units

Relative intensity

Comparison of one sound's intensity with a reference intensity

Decibel

Logarithmic expression of a ratio or relative level

Why decibels are used

Because acoustic values cover a huge range and logs make them easier to handle

Inverse square law

Intensity decreases in proportion to the square of distance from the source

Inverse square law example

If distance doubles, intensity becomes one fourth

Hearing range for frequency from slides

About 20 Hz to 20 kHz

Hearing range for intensity from slides

About 0 dB to 140 dB

Octave band

Frequency band spanning a two-to-one range of frequencies

Scientific notation

Number written as a coefficient between 1.00 and 9.99 times 10 raised to a power

Coefficient

The number between 1.00 and 9.99 in scientific notation

Conventional notation

Standard written form of numbers

Example of scientific notation

250000000 = 2.5 x 10^8

Negative exponent

Means the decimal was moved right to create the coefficient

Logarithm relationship

If x^y = z, then log base x of z = y

Antilog

Reverse of the logarithm process

Nominal scale

Named categories with no numerical order

Ordinal scale

Ordered categories

Interval scale

Ordered scale with equal intervals but no true zero

Ratio scale

Ordered scale with equal intervals and an absolute zero

Complex periodic sound

A sound with multiple frequency components and a repeating pattern

Fundamental frequency

The lowest frequency component in a complex periodic sound

f0

Symbol for fundamental frequency

Harmonics

Frequency components that are integer multiples of the fundamental frequency

Fourier's theorem

A complex wave can be represented as a sum of simple sinusoids differing in amplitude, frequency, and phase

Fourier analysis

Process of decomposing a complex wave into sinusoidal components

Frequency-domain appearance of complex periodic sound

Evenly spaced spectral peaks with a picket-fence appearance

Auditory impression of complex periodic sound

Musical

Sawtooth wave

Complex periodic wave with energy at all harmonics, odd and even

Sawtooth harmonic pattern

Harmonic amplitude decreases as 1 divided by harmonic number

Square wave

Complex periodic wave with energy only at odd harmonics

Triangular wave

A named type of complex periodic wave

Pulse wave

Another named type of complex periodic wave

Sawtooth example

If f0 = 4 V, then second harmonic = 2 V, third = 1.33 V, fourth = 1.0 V

Undistorted signal

A signal whose waveform is reproduced faithfully

Distorted signal

A signal whose waveform shape is altered

Three types of distortion in slides

Frequency distortion, transient distortion, amplitude distortion

Frequency distortion

Different frequencies are not reproduced with the same amplitude

System transfer function

The amplitude response of a system across frequency

Why system transfer function matters

It shows evidence of frequency distortion

Linear system

A system where output changes proportionally with input

Key property of linear system

Output amplitude does not have to equal input amplitude but must change proportionally

Transient distortion

Distortion related to the finite duration of a signal

Amplitude distortion

Distortion caused by nonproportional input-output amplitude behavior

Nonlinear system

A system where output does not change proportionally with input

Difference limen

Smallest perceivable difference between two sounds

JND

Just noticeable difference

Absolute DL

Actual amount of change needed to detect a difference

Relative DL

Absolute DL divided by the starting value

Weber fraction

Relative DL expressed as ΔI divided by I

Weber fraction example

If I = 1000 and ΔI = 50, then Weber fraction = 0.05

Frequency DL

Smallest detectable frequency difference

Relative frequency DL

Δf divided by f

Example frequency DL

If a 1000 Hz tone must change by 3.6 Hz, then absolute DL = 3.6 Hz and relative DL = 0.0036

Three dimensions of differential sensitivity

Intensity, frequency, and duration

Intensity DL

dB change needed to create a just noticeable loudness change

Important note about intensity and loudness

Increase in intensity is not always equal to the same increase in loudness

Binaural summation

Improved sensitivity and greater loudness when both ears are used together

Binaural beats

Perceived beats caused by neural interaction when slightly different frequencies are presented to opposite ears

Pitch

Auditory attribute by which sounds can be ordered on a musical scale

Pitch is the psychological correlate of

Frequency

High frequency sounds are perceived as

High pitch

Low frequency sounds are perceived as

Low pitch

Pitch of a pure tone

Corresponds to its frequency

Pitch of a periodic complex tone

Usually corresponds to the fundamental frequency

Not all pitch changes are perceptible

Pitch discrimination has limits and relates to DLF

Law of reflection for sound

Angle of reflection equals angle of incidence measured from the perpendicular