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
-those intended for sound reinforcement systems, public address systems, and home use.
General-purpose Microphones
Echo and Reverberation Equations
Stephen & Bate Equation
Sabine Equation
Norris-Erying Equation
Fitzroy Equation
those intended for laboratory measurement of acoustic pressure. These microphones must be very accurate and highly stable.
Measurement Microphones
–in this type of microphone, conversion of acoustic energy to electrical energy occurs because the sound pressure causes small motions of the microphone diaphragm.
Condenser Microphones
–these microphones are very similar to the condenser microphone; the main difference is that the externally applied bias voltage is eliminated through the use of a polarized material referred to as an electret.
Electret Microphones
–it is a resistive sensor that has been used over the years extensively in situations where it is acceptable to trade a high sensitivity for a poor linearity.
Carbon Microphones
these microphones rely on piezoelectric materials for the fundamentally linear conversion of mechanical energy to electrical energy.
Piezoelectric Microphones
–moving-coil electrodynamic microphones are the sensor counterpart of conventional electrodynamic loudspeakers.
Dynamic Microphones
–are quite similar to moving-coil electrodynamic microphones, but the diaphragm and the coil are replaced by a corrugated ribbon suspended in the gap of the magnetic circuit.
Ribbon Microphones
is the time required for the mean square sound pressure of a given frequency in an enclosure, initially in a steady state, to decay after the source is stopped, to 60dB or one-millionth of its initial value.
Reverberation time
–a room designed to suppress internal sound reflections as much as possible.
Anechoic chamber
–a distortion produced by combining an electrical or acoustical signal with a delayed replica of itself.
Comb Filter Effect
In this type of microphone, sound is incident on a diaphragm attached to a plunger that applies a force to carbon granules.
Carbon Microphones
–a measure of the efficiency of a surface or material in absorbing sound.
Absorption Coefficient
the distortion of a signal detectable by the ear.
Coloration of sound –
–the ability of a driver to send the sound waves out in a wide path.
Dispersion
–a graph showing the correlation of one signal with another
Correlogram
–a room in which the floor, ceiling, and wall are lined with a sound absorbing material to reduce reflections of sound to a minimum. It is also known as anechoic room or free-field room.
Dead Room
–also called Precedence Effect. Delayed sounds are integrated by the auditory apparatus if they fall on the ear within 20–40ms of the direct sound.
Haas Effect
a loudspeaker designed to reproduce middle-frequency sounds.
Driver
–the distortion of a wavefrontcaused by the presence of an obstacle in the sound field.
Diffraction of sound
-a proprietary sound-absorbing/ diffusing unit for use in corners of rooms
Korner Killer
–a ratio between the sudden drop of sound intensity from its loudest level to its softest level.
Dynamic Range
–a divider board used to separate the sound pressure areas in order to reduce the cancellation of sound.
Baffle
–a repetitive echo set up by parallel reflecting surfaces.
Flutter echo
–the ave.distance traveled between successive reflections
Mean free path
–an acoustical treatment plan for rooms in which one end is highly absorbent and the other end reflective and diffusive.
Live end Dead end
–the first wavefrontfalling on the ear determines the perceived direction of the sound.
Law of the First Wave front
–a delayed return of sound that is perceived by the ear as discrete sound image
Echo
–sound generated by air turbulence as it passes through ductwork and air control devices. It increases with an increase in air velocity.
Regenerated sound
-a proprietary device for the diffusion of sound through reflection phase-grating means.
Diffusor
Total Sound Power Level (PWLT) in dB
From Sources with Unequal Levels:
PWLT= __________
10 log WT+ 120
–a loudspeaker type that is used to transform sound energy having a high pressure and low velocity to sound energy having a low pressure and high velocity.
Horn
–a plot of frequency vs. sound pressure level in dB on standard NC chart.
Noise Criteria
–the interval between two frequencies having a ratio of 2:1.
Octave
–a reactive, tuned sound absorber; it is an air cavity within a massive enclosure, connecting to the surroundings by a narrow neck opening.
Helmhotz Resonator
–the study of the interaction of the auditory system and acoustics
Psychoacoustics
–the bending of sound waves travelling through layered media with different sound velocities.
Refraction of sound
TYPES OF SERVICES
- Aeronautical Fixed Service
- Aeronautical Mobile Service
- Aeronautical Mobile-Satellite Service
- Aeronautical Radio navigation Service
- Aeronautical Radio navigation-Satellite Service
- Amateur Service
- Amateur-Satellite Service
- Broadcasting Service
- Broadcasting-Satellite Service
- Earth Exploration-Satellite Service
- Fixed Service
- Fixed-Satellite Service
- Inter-Satellite Service
- Land Mobile Service
- Land Mobile-Satellite Service
- Maritime Mobile Service
- Maritime Mobile-Satellite Service
- Maritime Radio navigation Service
- Maritime Radion avigation-Satellite Service
- Meteorological Aids Service
- Meteorological-Satellite Service
- Mobile Service
- Mobile-Satellite Service
- Port Operations Service
- Radio Astronomy Service
- Radio determination Service
- Radio navigation Service
- Radio navigation-Satellite Service
- Safety Service
- Ship Movement Service
- Ship Operation Service
- Space Research Service
- Special Service
- Standard Frequency & Time Signal Service
- Standard Frequency & Time Signal-Satellite Service
–the loss of hearing sensation due to the thickening of the eardrum usually at old age.
Presbycosis
–is a graph wherein time is plotted in the x-axis, frequency is plotted in the y-axis, and the sound level is indicated roughly by the density of the trace.
Sound spectograph
-the maximum sound pressure which the human ear understands without discomfort of pain.
Threshold of Pain
–a large loudspeaker that reproduces low audio frequencies at relatively high power level.
Woofer
–one of a group of frequencies not necessarily harmonically-related to the fundamental, which appears in complex tones.
Partial
–a range of sound measure which the human ear can understand without discomfort or pain or evoke an auditory sensation.
Threshold of tolerance
–a high-pitch ringing
Tinnitus
–a loudspeaker designed to reproduce high-frequency sounds
Tweeter
–a room designed to emphasize reverberations. It is the converse of a dead room.
Reverberation Room
TYPES OF STATIONS
- Aeronautical Station
- Aeronautical Fixed Station
- Aircraft Station
- Amateur Station
- Base Station
- Broadcasting Station
- Coast Station
- Commercial Receiving Station
- Experimental Station
- Fixed Station
- Land Mobile Station
- Mobile Station
- Mobile Portable Station
- Portable Station
- Radio Direction-Finding Station
- Radio Training Station
- Radio beacon Station
- Radio location Station
- Radio navigation Station
- Radio navigation Land Station
- Ship Station
- Standard Frequency & Time Signal Station
- Transmitting Station
–a baffle with two openings at the front in which the back pulsations are bounced back and forth through a maze of small internal boxes.
Labyrinth Baffle
Types of Baffles
1.
3.
Bass Reflex
Infinite Baffle
Labyrinth Baffle
–a resonance condition in an enclosed space in which sound waves traveling in one direction interact with those traveling in the opposite direction, resulting in a stable condition.
Standing Wave
-in this type of baffle, the wave from the back of the diaphragm is isolated from the front wave, except that internal reflections may bounce back through the diaphragm or set-up secondary vibrations of the box itself. It is also known as closed box.
Infinite Baffle
-Refers to the airborne transmission of electromagnetic audio signals (radio) or audiovisual signals (television) that are readily accessible to a wide population via standard receivers.
BROADCASTING
–a loudspeaker baffle that has an opening dimension below the loudspeaker so that the bass frequencies from the rear emerge to reinforce those radiated directly forward.
Bass Reflex
– refers to that period of time between 2100 GMT – 1000 GMT (5:00AM – 6:00PM local standard time).
Daytime
– the greatest percentage of modulation that may be obtained by a transmitter without producing in its output harmonics of the modulating frequency in excess of those permitted by these regulation.
Maximum percentage of modulation
– refers to that period of time between 1600 GMT – 2100 GMT (12 midnight – 5:00 AM local standard time).
Experimental period
– refers to that period of time between 1000 GMT – 2100 GMT (6:00PM – 5:00AM local standard time).
Nighttime
– the carrier frequency authorized by NTC.
Authorized Frequency
– the effective value of the harmonic voltages present in the audio frequency output of the equipment under test.
Total Harmonic Distortion (THD)
– a sinusoidal voltage or current generated in a transmitter and subsequently modulated by a modulating wave.
Carrier wave
– the ratio of half the difference between the maximum and minimum amplitude of the AM wave to the average amplitude express in percentage.
Percentage of Modulation
– the power that is actually supplied to the radio station
Operating Power
– the frequency of the carrier wave.
Carrier Frequency
– a station operating on any one channel and is designed to render service over a primary service area which is limited by the subject to such interference as maybe received from a clear channel station.
Secondary Station
– the area in which the ground wave field of 3.16 mV/m (70 dBu) is not subject to objectionable interference or objectionable fading.
Primary Service Area
– the area receiving service from the ground wave but beyond the primary service area and subject to some interference and fading
Intermittent service area
– the area served by the skywave and not subject to objectionable interference. The signal is subject to intermittent variations in intensity.
Service Area
– the maximum power at which the transmitter can be operated satisfactorily and is determined by the design of the transmitter.
Maximum Rated Carrier Power
– the emission of any frequency outside of the assigned channel or authorized band of frequency and tolerances allowed by these regulations.
Spurious Emission
The frequencies are assigned at _______ interval
10 kHz
The allocation might be: is indicated by small letters
secondary allocation
▪ An entry of the time the station begins to supply power to the antenna and time it stops.
▪ An entry of the time the program begins and ends.
▪ An entry of each interruptions
▪ An entry of the following every 30 minutes: operating constants and antenna current.
Operating Log Entries
REGULATING BODIES
A number of standards bodies work on standards for frequency allocation, including:
▪International Telecommunication Union (ITU)
▪European Conference of Postal and Telecommunications Administrations (CEPT)
▪Inter-American Telecommunication Commission (CITEL)
Initially developed Arc Transmitter in 1903
Valdemar Poulsen
The allocation might be: is within the responsibility of administrations
exclusive or shared utilization
▪ An entry of the time each station identification announcement is made.
▪ An entry briefly describing each program broadcast.
▪ An entry showing that each sponsored program broadcast has been announced as sponsored
▪ An entry showing, for each program of network origin, the name of the network originating the program
Program Log Entries
credited as the primary developer of AM technology
Raginald Fessenden
The Amplitude Modulated (AM radio) carrier frequencies are in the frequency range of ___________.
535 - 1605 kHz
“undamped waves” are now called as
continuous waves
AM BROADCAST OPERATING REQUIREMENTS
Operating Schedule
Program Log Entries
Operating Log Entries
In what year an American established the first AM station
1924
The earliest public radiotelegraph broadcasts were provided as government services, beginning with daily time signals inaugurated on ________, by a number of U.S. Navy stations.
January 1, 1905
On _________, Nathan Stubblefield gave a short-range “wireless telephone” demonstration that included simultaneously broadcasting speech and music to seven locations throughout Murray, Kentucky.
January 1, 1902
On _________ a London publication, The Electrician, noted that “there are rare cases where, as Dr. Oliver Lodge once expressed it, it might be advantageous to ‘shout’ the message, spreading it broadcast to receivers in all directions”.
October 1898
Transmission of radio and television programs from a radio or television station to home receivers by radio waves is referred to as________________ and in most countries requires a broadcasting license.
“over the air” (OTA) or terrestrial broadcasting
-a low-frequency flutter
Wow
