Yamaha NEXO Alpha & Alpha E Series Owner's Manual download pdf (Page 13)

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ALPHA ARRAYS - SOME BASIC RULES

ALPHA SERIES USER MANUAL V1.0

DATE: 14/01/00 18:27

Hygrometry and Temperature - Air Absorption

Under usual conditions, air absorption increases when relative humidity decreases and increases

when temperature decreases.

Air absorption gives a linear attenuation, i.e. a constant value of loss of dB per meter: if 1 dB is lost

from 10 to 20 meters, 2 dB will be lost from 20 to 40 meters, 4 dB from 40 to 80 meters and so on...

The tables below list these values for normalised frequencies, and various values of relative

humidity and temperature:

At 20°C:

[dB] loss / meter Up to 1 kHz 2 kHz 4 kHz 8 kHz 16 kHz

RH 20% 0 0.02 0.06 0.20 0.66

RH 50% 0 0.01 0.03 0.08 0.27

RH 80% 0 0.00 0.02 0.05 0.17

Air absorption over a 50m distance; RH=20%-50%-80%

At RH 50%:

[dB] loss / meter Up to 1 kHz 2 kHz 4 kHz 8 kHz 16 kHz

10°C 0 0.01 0.04 0.13 0.43

20°C 0 0.01 0.03 0.08 0.27

30°C 0 0.01 0.02 0.06 0.19

20 100 1k 10k 20k

FREQ(Hz)

-40.00

-30.00

-20.00

-10.00

0.0

10.000

LEVEL(dBV)

AUDIO PRECISION vs 17 JUL 97 19:30:05

Air absorption over a 50m distance; t=10°C-20°C-30°C

The speed of sound C varies with temperature according to the formula below:

273 t20 C +°=

Where t° is the temperature in °C

The delay time between two sources spaced at a distance d is then:

∆t = C/d

20 100 1k 10k 20k

-40.00

-30.00

-20.00

-10.00

0.0

10.000

Frequency (Hz) / Attenuation (dB)

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 37 38

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Yamaha NEXO Alpha & Alpha E Series Owner's Manual Page 13

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