Audio/Acoustics
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Revision as of 12:02, 7 November 2007
Jump to: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Contents |
A
absolute pitch
Absolute pitch (ger. Absolutes Gehör) is the ability to identify the musical note (frequency) of a clear sine tone without an external reference.
- Remark: The allowed variance has to be defined.
- Remark: Mostly a musical note is identified not a frequency value.
adaptation
Adaptation (ger. Adaption) ...
B
bandwidth
The nominal bandwidth (ger. Bandbreite) of a filter is given by the difference between the upper and the lower cut-off-frequency. This difference may be expressed (1) in Hertz, (2) as percentage of the center frequency of the pass-band or (3) as the interval defined by the upper and lower cut-off-frequency in octaves (i.e. 1 octave, 1/3 octave)
- Remark: For more definitions see also USA Standard Method for Specifying the Characteristics of Analyzers Used for the Analysis of Sounds and Vibrations, Z24.15-1955
band power level
The band power level (ger. Band-Leistungspegel) of a sound for a specific wave band is the sound power level of a sound within a limited wave band.
band pressure level
The band pressure level (ger. Band-Schallpegel) of a sound for a specific wave band is the sound pressure level of a sound within a limited wave band.
- Remark: The wave band may be specified by its lower and upper cut-off-frequency or by its pass-band and the bandwidth. The bandwidth of the band may be specified as follows: octave-band (sound) pressure, half-octave-band pressure, third-octave-band pressure, 50-Hz-band pressure.
C
cut-off-frequency
The cutoff frequency (ger. Grenzfrequenz, Eckfrequenz) is the frequency nearest to the center frequency where the level exceeds ±3dB.
D
E
F
forward masking
(ger. Nachverdeckung): see also "masking".
G
H
I
K
L
M
N
neper
Neper (Np) (ger. Neper) is a unit used to express ratios, such as gain, loss, and relative values.
- The neper is analogous to the decibel, except that the Naperian base e (2.718281828...) is used in computing the ratio in nepers.
- The value in nepers, Np, is given by Np = ln(x1/x2), where x1 and x2 are the values of interest, and ln is the natural logarithm, i.e., logarithm to the base e.
- One neper (Np) = 8.686 dB, where 8.686 = 20/(ln 10).
- One dezibel (dB) = 0.1151 Np, where 0.1151 = ln(10)/20.
- The neper is often used to express voltage and current ratios, whereas the decibel is usually used to express power ratios.
- Np is a dimensionless unit (like dB).
- The ITU recognizes both units.
nominal bandwidth
See #bandwidth
O
R
reverberation
Reverberation (ger. Nachhall) is all sound due to reflexions measured in a closed system (room) after the sound source has stopped activity.
reverberation time
The reverberation time (ger. Nachhallzeit) is defined as the time needed the sound level reaches -60dB of average active sound level after stopping the sound source.
S
T
U
V
W
Z
References
- [ANSI] American National Standard Psychoacoustical Terminology (1973): ANSI S3.20-1973; Approved December 5, 1973; American National Standard Institute, Inc.
- [YOST] Yost, William A. & Donald W. Nielsen (1977): Fundamentals of Hearing. An Introduction. Holt, Rinehart and Winston; New York.