MidTerm Summary Flashcards
is one of regular vibration, of one or more definite frequencies. It contains, in addition to a fundamental frequency, higher tones that are harmonics of the fundamental frequency.
Musical sound
is an alteration in pressure, stress, particle displacement, or particle velocity that is propagated in elastic material.
Sound or a sound wave
The subjective unit of loudness is the
Sone
The human ear is sensitive to waves in the frequency range from about, called the audible range.
20 to 20,000 Hz
is the sensation produced through the ear by the sound wave alterations
Sound sensation
Types of Ordinary Sound
- Speech
- Music or Musical Tone
- Noise
is the science of sound including its production, propagation, and effects.
Acoustics
contains a complex mixture of sounds, some (but not all) of which are in harmonic relation to one another.
Speech
is sound of irregular vibration, or no definite range of frequencies. It consists of a mixture of many different frequencies within a certain range
Noise
The ______________ is a measure of the number of waves passing given point in 1 second.
frequency of a sound wave
that attribute of auditory sensation in terms of which sound may be ordered on a scale primarily related to frequency.
Pitch
the quality of sound related to its harmonic structure.
Timbre
is an observer’s auditory impression of the strength of a sound and is associated with the rate at which energy is transmitted to the ear.
Loudness
The distance between two successive crests of the wave is called the
wavelength
Intensity also depends on the __________ of the source from the observer.
distance
Attributes or Characteristics of Sounds
Pitch
Timbre
Loudness/Intensity
Phon =
40 + 10 log2 (Sone)
A ______ generates a bright sound and a jagged waveform.
violin
Sound Power Level (PWL) in dB
From an Isotropic Source in Free Space:
PWL = _________________
SPL + 20 log d + 11
The__________ produces a mellow, true sound and a relatively curved waveform.
flute
The maximum distance a wave travels from the normal, or zero, position is the
amplitude
is the characteristic of sound waves that we perceive as volume.
Amplitude
A______ makes a pure sound, vibrating regularly in a curving waveform.
tuning fork
Speed of sound in Various Bulk Materials Materials
Material Speed of Sound (m/s)
Water (0°C) ____________
1402
The _____ is the number of cycles, or oscillations, a sound wave completes in a given time.
frequency of a sound
The product of the wavelength and the frequency must equal the
speed of propagation of the wave
Speed of sound in Various Bulk Materials Materials
Material Speed of Sound (m/s)
Air (20°C) ______________
344
Speed of sound in Various Bulk Materials Materials
Material Speed of Sound (m/s)
Water (20°C) _________
1482
–the root mean square (rms) of the instantaneous sound pressure in a stated frequency band and during specified time interval, unless another time-averaging process is indicated, expressed in N/m2(Pa)
Sound Pressure
Speed of Sound in a Solid
V = sqroot (Y/ρ)
Speed of Sound in Gases
V= ______________
V = sqr root of (ˠRT/M)
the radiated acoustic power in a stated frequency band expressed in Watts (W).
Sound Power
–ten times the common logarithm of the ratio of the sound power to the reference sound power, Wo, (10-12 W) expressed in decibel (dB)
Sound Power Level
Sound Power Level (PWL) in dB
From a Source at Ground Level:
PWL = __________________
SPL + 20 log d + 8
SPL = _____________
20 log P + 94
a delayed return of sound that is perceived by the ear as a discrete sound image.
Echos
From Sources with Equal Levels:
PWLT= ___________
10 log n + PWL
Sound Pressure Level (SPL) in dB
From a source at ground level
SPL = ____
PWL –20 log d –8
Classes of Microphone Applications
Communication Microphones
Sound Recording & Broadcasting Microphones
General-purpose Microphones
Measurement Microphones
–ten times the common logarithm of the square of the ratio of the sound pressure to the reference sound pressure, Po, (20 µPa) expressed in decibel (dB)
Sound Pressure Level
Speed of Sound in a Fluid
V = sqroot(B/ρ)
–the output impedance of the microphone which determines the amplification methods that are suitable.
Electrical Characteristics
Types of Microphone
Condenser Microphones Electret Microphones Piezoelectric Microphones Dynamic Microphones Ribbon Microphones Carbon Microphones
–ten times the common logarithm of the ratio of the sound intensity to the reference sound intensity, Io, (10-12 W/m2) expressed in dB.
Sound Intensity Level
is the tailing off of sound in an enclosure because of multiple reflections from boundaries.
Reverberation
–the average rate of sound energy transmitted in a specified direction through a unit area normal to this direction at the point considered.
Sound Intensity
–is concerned with the behavior of sound within an enclosed space with a view to obtaining the optimum effect on the occupants.
Room Acoustics
An ______ is a reflected sound wave.
echo
SIL = ___________
10 log I + 120
This microphone exhibit poor linearity and poor dynamic range but are very rugged. They are poor choice of microphone for high-humidity environments, as the carbon granules coalesce.
Carbon Microphones
Properties of Microphones
Electroacoustic Performance
Electrical Characteristics
Sensitivity to External Influences
Cost
those intended for high-fidelity reproduction of speech and music.
Sound Recording & Broadcasting Microphones
–the ability of the microphone to perform task for which it was designed, generally measured in terms of its sensitivity, directivity, frequency response, transient response, linearity, SNR, and dynamic range.
Electroacoustic Performance
–the ability of the microphone to operate independently of the air temperature, relative humidity, and wind speed.
Sensitivity to External Influences
is a succession of echoes.
Reverberation
We also use the term sound for similar waves with frequencies above (______) and below (________) the range of human hearing.
ultrasonic, infrasonic
Sound Pressure Level (SPL) in dB
From an Isotropic Source in free space
SPL = _______
PWL –20 log d -11
those intended for speech communication between a small no. of individuals. Examples include telephone microphones & hearing aids
Communication Microphones