Handbook for Sound Engineers

1666 Chapter 48

48.9 Audio Frequency Range

The audio spectrum is usually considered the frequency
range between 20 Hz and 20 kHz, Fig. 48-10. In reality,
the upper limit of hearing pure tones is between 12 kHz
and 18 kHz, depending on the person’s age and sex and
how well the ears have been trained and protected
against loud sounds. Frequencies above 20 kHz cannot
be heard as a sound, but the effect created by such
frequencies (i.e., rapid rise time) can be heard.

The lower end of the spectrum is more often felt than
heard as a pure tone. Frequencies below 20 Hz are diffi-
cult to reproduce. Often the reproducer actually repro-
duces the second harmonic of the frequency, and the
brain translates it back to the fundamental.

48.10 Common Conversion Factors

Conversion from U.S. to SI units can be made by multi-
plying the U.S. unit by the conversion factors in Table
48-8. To convert from SI units to U.S. units, divide by
the conversion factor.

Table 48-8. U.S. to SI Units Conversion Factors

U.S. Unit Multiplier SI Unit

Length

ft 3.048 000 × 10–^1 m

mi 1.609 344 × 10^3 m

in 2.540 000 × 10–2 m

Area

ft^2 9.290 304 × 10–2 m^2

in^2 6.451 600 × 10–^4 m^2

yd^2 8.361 274 × 10–1 m^2

Capacity/volume

in³ 1.638 706 × 10–5 m³

ft³ 2.831 685 × 10–2 m³

liquid gal 3.785 412 × 10–3 m³

Volume/mass

ft³/lb 6.242 796 × 10–2 m³/kg

in³/lb 3.612 728 × 10–5 m³/kg

Ve l o c i t y

ft/h 4.466 667 × 10–5 m/s

in/s 2.540 000 × 10–2 m/s

mi/h 4.470 400 × 10–1 m/s

Mass

oz 2.834 952 × 10–2 kg

lb 4.535 924 × 10–1 kg

Short Ton (2000 lb) 9.071 847 × 10^2 kg

Long Ton (2240 lb) 1.016 047 × 10^3 kg

Mass/volume

oz/in³ 1.729 994 × 10^3 kg/m³

lb/ft³ 1.601 846 × 10^1 kg/m³

lb/in³ 2.767 990 × 10^4 kg/m³

lb/U.S. Gal 1.198 264 × 10^2 kg/m³

Acceleration

ft/s^2 3.048 000 × 10–1 m/s^2

Angular Momentum

lb f^2 /s 4.214 011 × 10–2 kg.m^2 /s

Electricity

A•h 3.600 000 × 10^3 C

Gs 1.000 000 × 10–4 T

Mx 1.000 000 × 10–8 Wb

Mho 1.000 000 × 10^0 S

Oe 7.957 747 × 10^1 A/m

Energy (Work)

Btu 1.055 056 × 10^3 J

eV 1.602 190 × 10–19 J

W•h 3.600 000 × 10^3 J

erg 1.000 000 × 10–7 J

Cal 4.186 800 × 10^0 J

Force

dyn 1.000 000 × 10–5 N

lbf 4.448 222 × 10^0 N

pdl 1.382 550 × 10–1 N

Heat

Btu/ft^2 1.135 653 × 10^4 J/m^2

Btu/lb 2.326 000 × 10^3 J/hg

Btu/(h•ft^2 •°F) or k (thermal

conductivity)

1.730 735 × 10^0 W/m•K

Btu/(h•f^2 •°F) or C (thermal

conductance)

5.678 263 × 10^0 W/m^2 •K

Btu/(lb °F) or c (heat capacity) 4.186 800 × 10^3 J/kg•K

°F•h•ft^2 /Btu or

R (thermal resistance)

1.761 102 × 10–1 K•m^2 /W

cal 4.186 000 × 10^0 J

cal/g 4.186 000 × 10^3 J/kg

Light

Cd (candle power) 1.000 000 × 10^0 cd

(candela)

fc 1.076 391 × 10^1 lx

fL 3.426 259 × 10^0 cd/m^2

Moment of Inertia

lb•ft^2 4.214 011 × 10–2 kg•m^2

Momentum

lb•ft/s 1.382 550 × 10–1 kg•m/s

Power

Btu/h 2.930 711 × 10–1 W

erg/s 1.000 000 × 10–7 W

Table 48-8. U.S. to SI Units Conversion Factors

U.S. Unit Multiplier SI Unit