Audio Engineering

Measurement 69

o r

In. .HF   In. .LF In 10 (xdecades .) (2.44)

Further,

HF..e()()xLFdecades    In^10 In.. (2.45)

a n d

LF..e[(In. .H F   x decades In^10 )]. (2.46)

Example
How many decades does the bandpass 500 to 12,500 Hz contain? Using Eq. (2-48),

In In

In

decades.

12 500 500

10

1 39794

,





If we had 12,500 Hz as a H.F. limit and wished to know the low frequency that would
give us 1.4 decades, we would calculate:

LF.. e

Hz.

 In decades In



[, (.  )]

12 500 1 4 10

497 63

If we had the L.F. limit and wished to know the H.F., then

HF.. e

Hz.

 decades In In



(.  ).

(, )

1 4 10 497 63

12 500

2.21 Defl ection of the Eardrum at Various Sound Levels ...............................................

If we make the assumption that the eardrum displacement is the same as that of the air
striking it, we can write

D

in f

LP

    310 

7 ⎛^1020

⎝

⎜⎜

⎜⎜

⎜

⎞

⎠

⎟⎟

⎟⎟

⎟⎟

(2.47)