Method has been devised to predict loudness level of any steady sound solely from its measured power spectrum level. Method is based on assumption that, with respect to loudness sensation, the human auditory system acts as open-loop transmission system with transmittance function determined from measured tone curves

Howes, W. L.

Lasalvia, E. A.

English

NASA Technical Reports Server

October 1972	 B72-10579 
NASA TECH BRIEF 
Lewis Research Center	
_4V 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Loudness (Annoyance) Prediction Procedure for

Steady Sounds 
A method has been devised to predict the loudness 
level of any steady sound solely from its measured 
power-spectrum level. For many applications, hand 
calculations are adequate; however, for applications 
involving considerable data, a computer program has 
been written to perform the loudness-level computation 
when the data consist of a 1/3-octave, power-spectrum-
level analysis of the noise (see note 4.). The method is 
based on the assumption that, with respect to the loud-
ness sensation, the human auditory system acts as an 
open-loop transmission system with a transmittance 
function determined from well-known, input-dependent, 
equal-loudness curves which are obtained by exposure 
of listeners to pure tones. (This differs from present 
methods wherein the transmittance function is often 
assumed to be independent of the stimulus intensity 
and is based on equal-loudness curves obtained by 
exposure to imprecisely specified bands of noise.). The 
transmitted power-spectral density is summed over all 
frequencies to obtain the overall loudness (annoyance) 
level. (This differs from most methods wherein loud-
ness, rather than power, in frequency bands is summed 
over all bands to obtain the overall loudness.) 
Because the sensations produced by sound stimuli 
in human beings are important to human existence and 
the development of human intellect, it is imperative in 
many endeavors ranging from sound reproduction (e.g., 
broadcasting) to transportation (e.g., pollution by noise) 
that the magnitudes of the sensations be quantified.
Any word which a listener might use to describe the 
subjective sensation produced by a sound constitutes a 
description of a psychological sensation which might be 
quantifiable. Possibly the most widely recognized audi-
tory sensation is "loudness." Loudness is defined as 
the magnitude of the auditory sensation produced by 
a sound stimulus. For annoying sounds, loudness is 
often a good measure of annoyance as well. 
The loudness of all sounds is specified relative to 
that of a 1-kiloHertz tone imposed on a listener from 
the front, as plane waves at a sound-pressure level of 
40 decibels. This reference sound and any other equally 
loud sound is said to have a loudness of 1 "sone." Like 
sound pressure, loudness is often expressed in logarithmic 
form and called loudness "level". The loudness level of 
any sound in "phons" is defined as being equal to the 
sound-pressure level of an equally loud, 1-kiloHertz 
tone. Thus, the loudness L and loudness level L of any 
sound are interrelated with the sound-pressure level S1 
of an equally loud, 1-kiloHertz tone according to 
L antiglog 10 [a(L.40)/10] 
L=S1 
where a is a constant (experimentally 1/3 al/2). 
The proposed method appears to be the only one 
which has, with good absolute accuracy, predicted the 
loudness and relative loudness of noises as judged by 
listeners. 
S
(continued overleaf) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000578 2020-03-17T03:35:48+00:00Z
Notes: 
This method should have application for prediction 
of loudness for a wide variety of situations such as 
noise suppression of jet engines, automobiles, trucks, 
and machinery, and for use in broadcasting, sound 
reproduction, speech analysis, and hearing aids. 
The following documentation may be obtained from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: NASA TM-X-2300, (N71.26993), 
Loudness Determined by Power Summation 
3. Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B72.10579
4. The computer program for use with this method may 
be obtained from: 
COSMIC 
112 Barrow Hall 
Univertity of Georgia 
Athens, Georgia 30601 
Reference: LEW-1 1761 
Patent status: 
NASA has decided not to apply for a patent. 
Source: Walton L. Howes
and Eileen A. LaSalvia 
Lewis Research Center
(LEW. l 1761) 
B72-10579	 Category 05, 09


Loudness (annoyance), prediction procedure for steady sounds

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