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The recent paper by Hueter et al. on ultrasonic lesions in the central nervous system, which appeared in a recent issue of this Journal (March, 1956), presents a rather limited view of this field and may lead to some misunderstandings.This note is a critical analysis of the Hueter paper. Some of the more important points discussed are: (1) The unique advantages of producing ultrasonic lesions in the brain by using dosages appropriate for selective action combined with focusing of the beam in contrast to the use of focusing alone. (2) The choice of an irradiation procedure in experiments designed for the elucidation of physical mechanisms of the action of ultrasound on tissue. (3) The specification of the acoustic variables required for a dosage description. (4) The inapplicability of Eyring's theory of viscosity, plasticity, and diffusion to the elucidation of observed dosage relations. (5) The clarification of the usage of the terminology, nontemperature effects. (6) The applicability of the reciprocity ...

A program for computer retrieval of papers in acoustics is being used to search titles of all papers that have appeared in four journals over the past 13 years. Title words and author surnames are truncated to five letters. The search may be weighted Boolean, fractional, or for associated words needed to formulate a request.

For several years we have used in this laboratory a set of steel bars, each mounted on a resonating box and respectively tuned to the frequencies 110, 220, 330, 440, 550, 660, 770, 880 and so on in the Fourier series, to and including 1760 c.p.s. This gives in effect it fundamental tone with the succeeding Fourier harmonics tip to the 16th inclusive. By repeated experiment with many students taking courses in the theory and practice of tuning pianos in equal temperament, during the last three years, we have found that, if we sound several of the bars simultaneously, choosing the members of the series in their regular succession, that is to say, such a series as 220, 330, 440, 550, 660, we always hear clearly and, as it were, beneath the simultaneous sounds, blended together into a chord, the fundamental tone 110. When again we take such a series as 440, 660, 880, 1100, we hear the fundamental 220. When we take 660, 990, 1320, 1560, we hear the fundamental 330. When again we have taken an irregular series,...

The use of thermosensitive paper is mooted in the design of an all‐purpose sound‐spectrum analyzer that would instantaneously and continuously provide both display and permanent graphic record. Some applications and extensions of the technique are suggested.

One of the central problems in auditory theory is to reconcile (a) the acute perception of slight changes in pitch displayed by the human listener with (b) the broad tuning of his cochlear analyzing mechanism. This paper attempts to describe and to relate a number of theoretical solutions to that problem. The hypotheses involve mechanisms, both mechanical and neural, for sharpening the analysis inherent in the cochlear transformation from frequency of stimulation to locus of vibration. These mechanisms operate in the domain of place—they are place theories that supplement the classical place theory. In a future paper, we plan to describe and discuss other sharpening mechanisms that operate in the domain of time.

The present paper compares four methods for measuring the speech‐quality parameter preference. The scales of the isopreference method, the category judgment method, the relative preference method, and the absolute preference judgment method (a proposed modification of the category judgment method) are related to a “preference unit” scale. Capabilities and performance of the methods are discussed and illustrated by evaluating a set of test signals with different types of degradation containing a subset of clearly discriminable signals. The paper tries to show how far preference results gained with one method allow prediction of corresponding results in terms of another method. Because of the quantitative limitations of subjective tests and especially since the four methods use different approaches and have different application ranges, it is not unexpected that the preference unit scale has been found to be more of scientific rather than of practical engineering interest. Listeners have been found capable of discriminating reliably, even without reference or anchor signals, more than the five quality steps provided by the category judgment method, and somehow also by the relative preference method. The proposed absolute preference judgment method recognizes this finding and, therefore, yields much better agreement with the isopreference method than the two other methods, which are apparently too strongly quantized.

This paper reviews the impact of digital computers on acoustics research since their introduction about a decade ago. The influential role that computers have attained in acoustics has resulted from their imaginative use as research tools for analysis, control of experiments, modeling, and simulation—rather than from straightforward calculating applications. Illustrative examples discussed in this paper include modeling of the human speech‐production process and the mechanical and neural aspects of hearing, speech analysis and synthesis, automatic speech and speaker recognition, generation of musical sounds and psychoacoustic test stimuli, study of the perceptual correlates of acoustic stimuli, multidimensional scaling, simulation of ray propagation in the deep ocean and in reverberant enclosures, acoustic measurements in concert halls, digital modeling of auditorium designs. Monte Carlo simulation of wave propagation in multimode transmission media, and acoustic image reconstruction of unknown objects by...

This paper is a preliminary report on the performance of a number of broadcast studios designed with convex plywood surfaces. Reverberation‐frequency characteristics, obtained by high speed level recorder, are presented as a basis for preliminary estimates of the absorption coefficient of the plywood cylinders. The effect of painting is estimated from studies on studios in various stages of finishing. Insofar as they are available, experiences of studio personnel in using these studios will be given in the paper.

In this paper experimental evaluation of a linear predictive speech compression system is described. A 10th‐order linear predictor is used assuming an all‐pole model. Input speech is bandlimited to 4 kHz and is sampled at 10‐kHz rate. Pitch synchronous analysis and synthesis is used. Transmission rate is constant but frame size, for which transmission parameters are sent, is time variant. An on‐line intelligibility measurement system [Agrawal and Lin, “An On‐Line Speech Intelligibility Measurement System,” IEEE Trans. Audio Electroacoust. AU‐22 (1974)] is used for PB word listening tests. This system uses a computer to administer the test, record the listener response, and automatically evaluate it on‐line. The compressed speech is bandlimited to 4 kHz. The intelligibility scores of 50 compressed PB words at different transmission rates are compared with original uncompressed PB words. This paper emphasizes the use of PB word intelligibility scores to improve the performance of linear predictive speech compression system. Statistical analysis of intelligibility scores and listener's response are reported. The results of quality comparison of compressed PB sentences at different bit rates are also reported.