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	;neper (Np) (ger. Neper): A unit used to express ratios, such as gain, loss, and relative values.		;neper (Np) (ger. Neper): A unit used to express ratios, such as gain, loss, and relative values.
-	* Note 1: The neper is analogous to the decibel, except that the Naperian base '''e''' (2.718281828...) is used in computing the ratio in nepers.	+	* The neper is analogous to the decibel, except that the Naperian base '''e''' (2.718281828...) is used in computing the ratio in nepers.
-	* Note 2: 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.	+	* 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.
-	* Note 3: One neper (Np) = 8.686 dB, where 8.686 = 20/(ln 10).	+	* One neper (Np) = 8.686 dB, where 8.686 = 20/(ln 10).
-	* Note 4: One dezibel (dB) = 0.1151 Np, where 0.1151 = ln(10)/20.	+	* One dezibel (dB) = 0.1151 Np, where 0.1151 = ln(10)/20.
-	* Note 5: The neper is often used to express voltage and current ratios, whereas the decibel is usually used to express power ratios.	+	* The neper is often used to express voltage and current ratios, whereas the decibel is usually used to express power ratios.
-	* Note 6: Like the dB, the Np is a dimensionless unit.	+	* Np is a dimensionless unit (like dB).
-	* Note 7: The ITU recognizes both units.	+	* The ITU recognizes both units.
	;nominal bandwidth: See ''Bandwidth''		;nominal bandwidth: See ''Bandwidth''

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Revision as of 09:36, 5 November 2007

Contents 1 A 2 B 3 C 4 D 5 E 6 F 7 G 8 H 9 I 10 K 11 L 12 M 13 N 14 O 15 R 16 S 17 T 18 U 19 V 20 W 21 Z 22 References

A

absolute pitch (ger. Absolutes Gehör)

absolute pitch is the ability to identify the 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 (ger. Adaptation)

B

bandwidth, (nominal bandwidth) (ger. Bandbreite)

The nominal bandwidth 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
• Remark: The cutoff frequency is the frequency nearest to the center frequency where the level exceeds ±3dB.

band power level (ger. Band-Leistungspegel)

The band power level of a sound for a specific wave band is the sound power level of a sound within a limited wave band.

band pressure level (ger. Band-Schallpegel)

The band pressure level 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

cutoff frequency (ger. Grenzfrequenz, Eckfrequenz)

The cutoff frequency 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 (Np) (ger. Neper)

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 (ger. Nachhall)

Reverberation is all sound due to reflexions measured in a closed system (room) after the sound source has stopped activity.

reverberation time (ger. Nachhallzeit)

The reverberation time 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.