Page 129 - The Master Handbook Of Acoustics

104 CHAPTER FIVE

Frequency Range of Speech and
Table 5-1 Power of Musical Sources. 5
Music
Instrument Peak, power (watts)
It is instructive to compare the frequency range
Full orchestra 70 of the various musical instruments with that of
Large bass drum 25 speech. This is best done graphically. Figure 5-11
Pipe organ 13
includes the ranges only of the fundamental
Snare drum 12
tones, and not of the harmonic tones of the
Cymbals 10
instruments. The very low piano and organ
Trombone 6
notes, which are below the range of audibility of
Piano 0.4
the ear, are perceived by their harmonics. Certain
Trumpet 0.3
high-frequency noise accompanying musical
Bass saxophone 0.3
Bass tuba 0.2 instruments is not included, such as reed noise
Double bass 0.16 in woodwinds, bowing noise of strings, and key
Piccolo 0.08 clicks and thumps of piano and percussion
Flute 0.06 instruments.
Clarinet 0.05
French horn 0.05 Future Dynamic-Range
Triangle 0.05
Requirements
If the peak instantaneous sound levels and noise
thresholds are regarded as determining dynamic
range requirements, much greater ranges are required. Fiedler’s study 6
has shown that a dynamic range of up to 118 dB is necessary for subjec-
tively noise-free reproduction of music (see Fig. 5-12). He considered the
peak instantaneous sound level of various sources, as shown at the top of
the figure, and the just-audible threshold for white noise added to the
program source when the listener is in a normal listening situation, as
shown at the bottom of the figure. He used musical performances of high
peak levels in a quiet environment and a very simple recording setup.
The results are summarized in Fig. 5-12. The signal-to-noise ratio offered
by a 16-bit PCM (pulse code modulation) system is shown to be inade-
quate for all but the piano solo. Future developments will undoubtedly
require greater dynamic range than that offered by 16-bit digital systems.

Auditory Area

The frequency range and the dynamic range of speech, music, and all
others sounds places varying demands on the human ear. The auditory
area back in Fig. 3-8 describes the capability of the ear. Both speech