Octave Band Analysis Research Articles

The use of noise-making toys as audiometric devices

For a considerable period of time in the literature concerned with pediatric audiology—or, more specifically, audiometry for infants—it has been suggested that one should or should not use measurable noise-making toys as stimulus devices. Proponents of their use suggest that they are intrinsically more attractive to infants and therefore enhance responsivity. Opponents of the use of such devices have based their claims on the idea that the signal produced by such devices are neither calibrated nor replicable. It is probably the case that both positions are correct, and this leaves the practitioner without expert advice. The study reported here is a simple electroacoustic evaluation of a set of such toys which are now commercially available. The experiment consisted of having two persons use each device 3 times according to the instructions provided with the materials. The toys consist of a bell, a horn, two rattles, and a squeaking toy. The signals produced by these several repetitions of the toys were subjected to one-third octave band analysis by a Bruel and Kjaer Model 2112 spectrometer. A result showed that the signals produced by these toys are indeed replicable, but generally have such flat spectra that they may not be selectively useful except as gross screening devices.

Fire fighter noise exposure.

Occupational noise exposure was evaluated for eight fire fighter positions on board three types of emergency vehicles. One hundred seventy code-3responses were monitored and sound pressure levels in excess of 115 dBA found. Futhermore, sound pressures exceeding the OSHA allowable level of 90 dBA for eight hours exposure were determined. Octave band analyses were performed for overall code-3 noise and for specific noise sources on each vehicle. An evaluation of eighty-nine audiograms of fire fighters was also carried out. The findings of this study suggest that under present operational conditions fire fighters experience excessive short-duration, high intensity noise exposure and a hearing conservation program for the fire service is therefore recommended.

Features of fully portable 1/3 octave real‐time analyzer

The 1/3 octave real‐time analyzer is used especially for research of evaluation or reduction of environmental noise and vibration. Since it has been very expensive, large, and heavy, and dependent on external power sources, users were limited and the field operation was difficult. We have newly developed fully portable 1/3 octave real‐time analyzer Model SA‐24, which has 3.5‐in. CRT display, measures 29(W) × 10(H) × 36(D) cm, weighs 8.5 kg and operates with internal rechargeable battery (about 4 hours continuous operation), AC line and external DC. The price has become as less expensive as 1/3 of other equivalent models. Model SA‐24 has plug‐in filters of multi‐channel covering 31.5 Hz through 8 kHz for 1/3 or 1/1 octave band analysis and 1 Hz through 250 Hz for 1/3 octave band analysis. The band level is detected by RMS detector at crest factor 3 (± 0.5 dB), and the averaging time constant can be selected between 0.1 s and 10 s. The dynamic range of level detection and display is over 40 dB, and instantaneous and maximum level hold can be made. The spectrum pattern can be read out to level recorder or to other instuments.

Container blow molding noise.

Evaluation of the environmental noise within a blow mold plant revealed borderline acceptability for hearing conservation. However, audiometric examinations did not appear to reveal appreciable work-related hearing loss. Octave band analysis of this nuisance noise provided the base for feasible engineering controls.

Methods of measuring and rating hearing protector performance.

This paper reviews various methods that have been used to measure and rate the performance characteristics of hearing protectors. Subjective and objective measurements methods will be discussed with respect to test method, environment and stimuli. A variety of methods for relating protector attenuation data to the requirements of a specific environment will be presented and discussed. The paper includes suggestions for use of this information with environmental data developed from octave band analysis or sound pressure level measured in dBA.

A basic study on the measurements of the percussion sound of the tooth (author's transl)

Much can be learned about the percussion sound of the tooth as a clinical diagnostic method of the periodontal condition.The aim of this article is to present the technique of recording sounds made by the tooth percussion and to discuss the significance in the diagnosis of the periodontal disease. Therefore, the author developed a measuring equipment for the percussion sound of the tooth, which consists of a microphon, a magnetic tape deck, a 1/3 octave band analyzer, an oscilloscope, and a camera.As a means of studying materials, three male subjects in possession of normal teeth and periodontal tissue are selected, and their sounds of percussing the teeth are recorded and measured by this equipment. The results of this study were as follows:1. For the purpose of determining quantity and discussing the percussion sound of the tooth, the author developed a new apparatus to percuss the tooth, and discussed a standardizing method of the “percussion sound trace”.2. The frequencies which constitute the percussion sound of the tooth are affected by the kinds of the percussion instruments.However the percussion sound has a fundamental frequency, and its range of fundamental frequency is about below 1250Hz.3. The peak-peak value of the percussion sound traces is much influenced by the magnitude of the load which percussed the tooth, but the attenuation time of it is less influenced by the load, and the value off fandamental frequency of its sound is little influenced by the load.

Predicting the Effectiveness of Auditory Warning Signals in Industrial Environments

A method is presented whereby the effectiveness of auditory warning devices in a given acoustical background can be predetermined and the most effective signal selected. In developing the methods, eight complex, variable pitch acoustically engineered horn-type signals were used. Four spectrally representative industrial noise backgrounds plus white noise were used to provide test environments. A predictive model involving octave-band analysis, signal-noise ratios and reaction time was developed.

“Square-wave stimuli” and neonatal auditory behavior: Some comments on Ashton (1971), Hutt et al. (1968) and Lenard et al. (1969)

Recent work reporting neonatal auditory responses to complex tones generated by applying electrical square-wave stimuli to loudspeakers is reviewed with reference to the nature of the acoustic stimulus. Attention is particularly drawn to the harmonic structure of such tones in relation to the nonlinear frequency response of small loudspeakers. A 1 3 - octave band analysis of some “square-wave tones” is given to illustrate the difficulties of interpreting the results of work using such complex stimuli. The findings of the previous studies are ascribed essentially to differences in the stimulus bandwidth, rather than to differences in audiofrequency, and difficulties apparently generated by using differences in stimulus bandwidth as the sole explanation are at least partially resolved.

Evaluation of methods used for converting octave band analyses to equivalent a-weighting levels.

The United States Department of Labor standards for employee exposure to noise specify that sound levels shall be measured with an instrument that operates on the A-weighting network, slow response. However, some instruments currently being used are not equipped to measure A-weighting levels. Thus, it becomes necessary to convert octave band levels to equivalent A-weighting values for correlation with the adopted standards. In this article, three methods of converting octave band analyses to A-weighting levels are evaluated.

Low frequency sound measurement in vehicles

Sound pressure level measurements in cars travelling at motorway speeds have shown that, in many cases, the overall level is very high in relation to the dB(A) and octave band levels, suggesting that much of the sound energy is in the low frequency and infrasonic regions. A technique has been developed to extend accurate octave band measurements down to the octave centred on 2 Hz. The system uses a calibrated sound level meter feeding a frequency modulation tape-recorder to record noise below 64 Hz, and an octave band analysis system to analyse the resultant tape recordings. Typical results are presented for a number of vehicles and it is found that sound pressure levels as high as 120 dB can be found in the octave bands between 2 and 16 Hz.

Vibration and Acoustic Signatures of a Rolling Element Bearing

An investigation was made of the vibration and acoustic response of an operating ball bearing under varying degrees of damage. This included defects on the inner and outer races, the bearing cage, and the rolling elements. Vibration and acoustic measurements were made simultaneously with a 6% octave band analyzer. The bearing was rigidly mounted with a press fit on its outer ring, simulating industrial practice. It was found that considerable energy, both acoustic and mechanical, is dissipated at the higher frequencies even in a satisfactory bearing. Moreover, the energy distribution within the two signatures is not similar. Thus, identification of machine faults by an acoustic measurement method is still questionable.

Clinical Study to Evaluate Rock Music, Symphonic Music, and Noise as Sources of Acoustic Trauma

Recent studies have implicated rock music as a potential source of hearing damage. The present study was designed to evaluate, under carefully controlled clinical conditions, the relative damage potential of rock music, symphonic music, and bandlimited white noise. Ten normal-hearing subjects were exposed to each program source for 60 min at an average SPL of 95 dB binaurally through electrostatic headphones. After each exposure a TTS5 was obtained by Békésy audiomerry at each of 10 frequencies. An octave-band analysis demonstrated that both the rock and symphonic music had very similar frequency spectra being within ±4 dB from 125 to 8000 Hz and having maxima at 500 Hz. The TTS5s for both rock and symphonic music were nearly identical with maximum TTS5s from 2000 to 5000 Hz and averaging 8–10 dB. The white noise, being richer in high frequencies, produced average TTS5s of 11–17 dB for the same test frequency range. Males showed generally higher TTS than females; for example the white-noise induced TTS5 at 4000 Hz was 22 dB for males and 11 dB for females. In conclusion symphonic music is just as potentially harmful as rock music if played at the same intensity and daily 1-h exposures at less than or equal to 100 dB SPL appear quite safe for the average listener.

A portable tape recorder for noise analysis.

A light-weight battery-powered tape recorder has successfully been adapted for noise analysis in the frequency range of 20 to 10,000 Hz. Minor circuit changes were necessary to obtain the desired flat response. The recorder, complete with rechargeable nickel-cadmium batteries and leather case, weighs 8.5 pounds. A 10-second recording provides adequate tape for the laboratory octave band analysis.

Electronic Evaluation of Prosthetic Cardiac Valve Performance.

Excerpt A new noninvasive technique, octave band analysis, has been used for measuring objectively the sound level energy in decibels (db) and cutoff frequency in Hertz (Hz) of prosthetic valve sou...

Interior Noise of Airline Aircraft

Data gathered with an octave band analyzer is reported for many of the currently operated propeller, turboprop, and jet airline aircraft. The investigation dealt primarily with noise associated with the cockpit environment, however, a number of noise profiles in the passenger cabin are presented. Two criteria are the basis for evaluating the environment: damage risk criteria and speech interference level. Almost all airline cockpits rely on the unaided voice to communicate commands and therefore interference with speech is critical. Even recent models of jet aircraft cause cockpit communications, in some regimes of flight, to be carried out at a near shout. Many of the relatively new turboprop aircraft exceed the damage risk criteria in the cockpit.

Studies on Air Pollution Caused by Automobile Exhaust Gases (Report I)

An investigation was made on noise and air pollution caused by automobiles passing Kanmon Tunnel from 9:30a.m. to 4:30p.m. on Feb. 26, 1964, The positon taken was at the centre of the tunnel. This tunnel is 3461.4m. in length and is one of the most important links between Honshu and Kyushu Islands of Japan. The investigations took place every 30 minutes and the following is the result.1) Three thausands two hundreds and eighty one autmobiles proceeded through the tunnel's entrance over 7 hour period. The expected increase is arise to a approximately 12, 000 per day by 1970.2) Suspended dusts in the tunnel were sampled by the “Roken Type Dust Sampler” like Owen's Jet Dust-Sampling Instrument and were counted using a microscope as is usual. The mean amount of Suspended dusts was 824/ml. of the air. More than 1000/ml. of dust was detected twice out of six times in the a.m., and 3 out of 8 times in the p.m. Such a condition is the most infavorable for laborers in the area.3) Concentrations of CO2 were examined twice every 30 munites using “Kitagawa's Indicator Sampler.”. The concentration of CO2 didn't reach a remarkable high level, but was between 0.05%-0.07%. The mean value of this test is 0.059%.4) Carbon Monoxide, an important part of the study of air pollution caused by automobiles, was checked regularly close to the entrance of the tunnel. The concentration of CO which was measured location was between 0.01% to 0.03% and the mean value was 0.03%.5) Sulfur dioxide in the air, which may be exhausted mainlyfr om diesel engines, was absorbed by the HgCl2-NaCl solution in a small impinger bottle. Next the concentration of SO2 was measured by colorimetry method using p-rosaniline and formaline as reagents. The mean concentration and the maximum concentration of this survey was 0.189 and 0.239p.p.m. respectively.6) Sound level was checked 5 times every 30 minutes using a sound level meter. Maximum sound level from trucks was 116 phon (A). The level of the back ground noise in the tunnel was between 82 phon (A) to 100 phon. As a result of octave band analysis, the over all sound level had a very high intensity and the main frequency of noise in the tunnel was composed of low frequency. The results of this investigation above sound level, concentrations of carbon monoxide and sulfur dioxide in this particular tunnel were unexpectedly over the normal range levels. Therefore, it can be concluded that an increase of ventilation volume should be undertaken while an attempt bema de to decrease the concentration levels of exhaust gases given off by the vehicles under consideration.

Characteristics of Typewriter Noise

Measurement of noises of short-time duration, such as typewriter noise, is not satisfactory when carried out using conventional sound level meters. Availability of an Impact Noise Analyzer allows measurement of peak levels and decay-time constants of typewriter noise. The measurement and evaluation of typewriter noise using this instrumentation is reported in this paper. Peak sound power levels due to type impact were found to be 90±5 db, with an average decay-time constant of 2–3 msec. Investigation of typewriter noises using this instrument also reveals that the decay-time constant is as important a parameter characterizing a short-time duration noise as is its peak level. Decay-time constants of noises due to different typewriter operations were found to vary from 2 msec to over 300 msec. Octave and third-octave band analyses of typing noise were also carried out using the Impact Noise Analyzer. The most important frequency bands of noise due to type impact were found to be those above 1200 cps. Relative energy of the noise in octave bands indicates that type impact noise, and the noise generated in the desk supporting the typewriter, are the most important sources of noise in typing. (This work was carried on in the General Research Laboratory of the Underwood Corporation, Hartford, Connecticut.)

Riveting Noise Study

A study of riveting noise in the aircraft industry has been made. Octave band analysis led to a statistical survey, where variations in sheet, thickness, rivet diameter, and Bucking bar were tried. Although design consideration will prevent us from eliminating major noise sources, some limited data are available in controllable factors which have significant influence on riveting noise level.

On the Interpretation of Certain Sound Spectra of Musical Instruments

The problem of computing sound power from measurements of average rectified sound pressure is reviewed, particularly in relation to “Absolute Amplitudes and Spectra of Certain Musical Instruments and Orchestras” published by Sivian, Dunn, and White in 1931. Experimental data on the distribution of instantaneous pressure amplitudes of music in a wide band and relations between rms and average pressure in octave and half-octave bands for speech are introduced; these data suggest, for example, that in a half-octave band in the vicinity of 1000 cps the rms sound-pressure level during a 15-sec interval of music exceeds the average pressure level by 9 db. Means are described for converting the old data based on “pressure per cycle” to a form that would be obtained with the modern octave band analyzer and sound level meter. In place of the steeply sloping spectra suggested by the original figures, the two kinds of corrections lead to an average sound power spectrum, for the 15-piece orchestra, having a broad peak between 100 and 4000 cps.

Reducing Noise in a Sugar Refinery

During a certain phase of sugar refining, low-pressure steam is allowed to flow from boilers into vacuum pipes. The flow is controlled by straightway valves which are normally only very slightly opened. Flow velocity in the pipes is of the order of 165 to 290 ft per second. A very shrill, painful, and permanent hissing noise was produced, accompanied by complaints from everybody in the factory. Investigations showed the valves to be the noise generators, and the pipes to be the radiators. The obvious solution was to use valves with smaller diameters and combine them with Venturi tubes. This could not be done for sugar technique reasons. The solution adopted was to place functional sound absorbers along and around the vacuum pipes. The results were that the over-all sound pressure level dropped only from 99 to 97 db. One-third octave band analysis showed marked improvements above 1000 cps. The workers unanimously declare that the noise “has disappeared” and that they do not suffer any more. It is not always necessary to reduce the over-all sound pressure level. Reducing the level in a few disturbing bands is easier and satisfactory.