Terms in this set (52)
sound pressure waves
Sound arrives at the ear in the form of periodic variations in atmospheric pressure
Likewise, as a vibrating mass (such as a guitar string, a person's vocal chords or a loudspeaker) moves outward from its normal resting state, it squeezes air molecules into a compressed area, away from the sound source. This causes the area being acted on to have a greater than normal atmospheric pressure
As the vibrating mass moves inward from its normal resting state, an area with a lower-than-normal atmospheric pressure will be created
sound wave itself moves through atmosphere in form of high-pressure compression waves that push areas of low pressure (in outward direction) the process is known for the outward pressure motion
waveform is essentially the graphic representation of a sound-pressure level or voltage level as it moves through a medium over time.
The distance above or below the centerline of a waveform (such as a pure sine wave) represents the amplitude level of that signal.
the measurement of either the maximum positive or negative signal level of a wave is called its peak amplitude value (or peak level).
peak to peak value
The total measurement of the positive and negative peak signal levels
root mean square
root-mean-square (rms) value was developed to determine a meaningful average level of a waveform over time
The rate at which an acoustic generator, electrical signal or vibrating mass repeats within a cycle of positive and negative amplitude is known as the frequency of that signal.
One completed excursion of a wave (which is plotted over the 360 ° axis of a circle) is known as a cycle
The number of cycles that occur within a second (frequency) is measured in hertz (Hz).
frequency is measured in Hertz
The velocity of a sound wave as it travels through air at 68 ° F (20 ° C) is approximately 1130 feet per second (ft/ sec) or 344 meters per second (m/ sec). This speed is temperature dependent and increases at a rate of 1.1 ft/ sec for each Fahrenheit degree increase in temperature (2 ft/ sec per Celsius degree).
The wavelength of a waveform (frequently represented by the Greek letter lambda, X) is the physical distance in a medium between the beginning and the end of a cycle.
period of wave
The time it takes to complete 1 cycle
frequency response curve
The charted output of an audio device is known as its frequency response curve
This curve is used to graphically represent how a device will respond to the audio spectrum and, thus, how it will affect a signal's overall sound.
flat frequency response curve
If the measured signal is the same level at all frequencies, the curve will be drawn as a flat, straight line from left to right (known as a flat frequency response curve). This indicates that the device passes all frequencies equally (with no frequency being emphasized or de-emphasized).
Variations of phase
Variations in phase, which are measured in degrees (°), can be described as a time delay between two or more waveforms.
Out of phase (example)
let's limit our example to two pure tone waveforms (sine waves) that have equal amplitudes and frequency, but start their cyclic periods at different times. Such waveforms are said to be out of phase
in phase the waves have no relative time difference),
Phase shift is a term that describes one waveform's lead or lag in time with respect to another . Basically, it results from a time delay between two (or more) waveforms (with differences in acoustic distance being the most common source of this type of delay).
sine wave , which is composed of a single frequency that produces a pure sound at a specific pitch.
The factor that helps us differentiate between instrumental "voicings" is the presence of frequencies (called partials) that exist in addition to the fundamental pitch that's being played.
Partials that are higher than the fundamental frequency are called upper partials or overtones.
overtone frequencies that are whole-number multiples of the fundamental frequency are called harmonics.
The ear perceives frequencies that are whole, doubled multiples of the fundamental as being related in a special way (a phenomenon known as the musical octave).
known to be pleasing to the ear (consonant)
even multiples of fundamental
displeasing to the ear (dissonant)
odd multiples of fundamental
Square waves, triangle waves and sawtooth waves are examples of simple waves that contain a consistent harmonic structure ( Figure 2.14 ). They are said to be simple because they're continuous and repetitive in nature.
often are not symmetrical about the zero line. (do not repeat)
Regardless of the shape or complexity of a waveform that reaches the eardrum, the inner ear is able to perceive these component waveforms and then transmit the stimulus to the brain.
anvil,stirrrup, hammer (these bones act as amp and protectant )
The harmonics and their relative intensities (which determine an instrument's characteristic sound) are called the timbre of an instrument.
Each one produces a sonic amplitude envelope that works in combination with timbre to determine its unique and subjective sound. The envelope (ADSR) of a waveform can be described as characteristic variations in level that occur in time over the duration of a played note.
Attack (A ) refers to the time taken for a sound to build up to its full volume when a note is initially sounded.
Decay (D ) refers to how quickly the sound levels off to a sustain level after the initial attack peak.
Sustain (S) refers to the duration of the ongoing sound that's generated following the initial attack decay.
Release (R) relates to how quickly the sound will decay once the note is released.
By using a compressor or limiter, an instrument's character can often be (b) modified by changing the dynamics of its envelope without changing its overall timbre.
The unit used for measuring sound-pressure level (SPL), signal level and relative changes in signal level is the decibel (dB), a term that literally means 1/ 10th of a Bell (an older telephone transmission loss measurement unit that was named after Alexander Graham Bell, inventor of the telephone).
. Turning something up by 3 dB will double the signal's level
The logarithm (log) is a mathematical function that reduces large numeric values into smaller, more manageable numbers.
In audio, we use logarithmic values to express the differences in intensities between two levels
log of number 2 is .03
sound pressure level (SPL)
SOUND-PRESSURE LEVEL Sound-pressure level is the acoustic pressure that's built up within a defined atmospheric area (usually a square centimeter, or cm2). the higher the SPL, the louder the sound
Voltage can be thought of as the pressure behind electrons within a wire.
Power is usually a measure of wattage or current and can be thought of as the flow of electrons through a wire over time.
part of outer ear
these variations arrive at the listener, sound-pressure waves are collected in the aural canal by way of the outer ear's
sound waves changed into mechanical vibrations and moved to inner ear
contains tiny hairs These hairs respond to certain frequencies depending on their placement along the organ , which results in the neural stimulation that gives us the sensation of hearing`
threshold of hearing
a convenient pressure-level reference is the threshold of hearing, which is the minimum sound pressure that produces the phenomenon of hearing in most people
threshold of feeling
An SPL that causes discomfort in a listener 50% of the time is called the threshold of feeling. It occurs at a level of about 118 dB SPL between the frequencies of 200 Hz and 10 kHz.
threshold of pain
The SPL that causes pain in a listener 50% of the time is called the threshold of pain and corresponds to an SPL of 140 dB in the frequency range between 200 Hz and 10 kHz.