**Nanomedicine,
Volume I: Basic Capabilities**

**©
1999 Robert A. Freitas Jr. All Rights
Reserved.**

Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999

**4.9.1.5 Vocalizations****
**

Average source power for conversational speech in air is ~10
microwatts at the vocal cords (60 dB), up to ~1000 microwatts for shouting (90
dB) and as little as 0.1 microwatts (30 dB) for whispering.^{3511}
Vocal cord surface area ~1 cm^{2}, giving an acoustic intensity I ~
0.001-10 watts/m^{2}. (Using the decibel notation, dB = 10 log_{10}
(I/I_{0}), where I_{0} ~ 5 x 10^{-13} watts/m^{2}
in air, I_{0} ~ 1 x 10^{-16} watts/m^{2} in water.)
In a planar traveling wave, pressure amplitude A_{p} (N/m^{2})
is related to power intensity I by

_{}
{Eqn. 4.53}

For water at 310 K, r = 993.4 kg/m^{3}
and v_{sound} = 1500 m/sec, therefore A_{p} = 0.0005-0.05 atm
for speech, detectable by nanodevices throughout the body due to minimal attenuation
at audible frequencies (Section 4.9.1.3). Other easily
detectable vocalizations include whistling, humming, coughing, sneezing, rales,
wheezing, expectorating, eructations, flatus, vomiting, hawking and noseblowing.

In the case of spherical waves diverging from an omnidirectional
transmitter of radius r at a distance X from the transmitter, average intensity
declines inversely as the square of the distance and so I in Eqn.
4.53 must be replaced by (I r^{2} / X^{2}).

Last updated on 17 February 2003