Audible Effects Research Articles

Using statistical decision theory to predict speech intelligibility. III. Effect of audibility on speech recognition sensitivity

The speech recognition sensitivity (SRS) model [H. Müsch and S. Buus, J. Acoust. Soc. Am. 109, 2896-2909 (2001)] is a macroscopic model for predicting speech intelligibility. The present study proposes a modification to the relation between the SRS model's audibility-noise variance and the signal-excitation to noise-excitation ratio (SNRE) in the auditory periphery. The modified relation is derived from data obtained in nine studies that measured normal-hearing listeners' consonant-recognition performance at several levels of speech-spectrum shaped noise. When the audibility-noise variance is directly proportional to the relative power of the noise excitation in the auditory periphery, the SRS model yields good predictions of the data. Four of the nine studies also reported consonant-recognition performance in various filtering conditions. Good predictions of these data were achieved with SRS model parameters that were consistent with the model parameters fitting the speech-in-noise data and with the model parameters used in the original SRS papers.

Talking doll having extendible appendages

A toy figure includes a generally spherical torso supporting a pair of outwardly extending sleeves which in turn receive a pair of slidably supported arms. A second pair of sleeves supported on the torso receive a pair of slidably supported legs. An additional sleeve is positioned upon the toy figure head and receives a slidably supported shaft having a ball member at its outer end. A plurality of switches are positioned within the toy figure and are actuated as the arms, legs and head shaft are moved inwardly and outwardly. A sound circuit is supported within the toy figure and is responsive to actuation of the various switches therein to produce audible message or sound effects. The toy figure head further supports a pair of ears slidably movable in a lateral direction within the head.

If you can’t take the room out of your mix, you can’t take your mix out of the room!

The key issue in any recording studio is transferability—the ability of a mix to transfer to other listening environments outside the studio. For a mix to faithfully transfer to a wide range of acoustical environments, it must be created in a room with minimal acoustic distortion. The music industry is very aware of electronic distortion; however, the audible effects of acoustic distortion are only now being fully appreciated. The four forms of acoustic distortion are modal coupling, speaker boundary interference response, comb filtering and poor diffusion or a sparse spatial and temporal reflection density. These phenomena will be explained and methods to minimize them will be suggested.

Tonal response on the stairway of the main pyramid at La Ciudadela, Teotihuacan archaeological site

This paper presents new research on the very interesting audible effects produced by the stairways of many archaeological sites in Mexico. This investigation was made at the main stairway of the pyramid at La Ciudadela, Teotihuacan archaeological site. The effect previously studied was a chirped echo reflected from the stairway at normal incidence, which resembles the singing of the Quetzal. Now it is presented with the impulsive sound source and the listeners located at different angles, where apart from the characteristic chirped sound, several musical notes could be obtained and identified, covering a range of at least one half an octave. This evaluation was made at the site, where the effect is clearly audible, and it is supported with simple mathematics.

Theoretical interpretation of a case study: Acoustic resonance in an archaeological site

It is well-known that the stairways of some Mexican archaeological sites, like Chichen-Itza or Teotihuacan, present an interesting sound reflection and resonance phenomenon which causes a special audible effect. In this paper, mathematical modeling of this situation is presented, and the practical phenomenon is discussed from a theoretical standpoint. More than an end in itself, the idea is, once this validated model is obtained, to use the results for the analysis of a more extensive architectural environment in order to establish whether this kind of phenomenon would have been purposely introduced in the design of the site. This will be presented in future publications.

Subband neural networks prediction for on-line audio signal recovery

In this paper, a subbands multirate architecture is presented for audio signal recovery. Audio signal recovery is a common problem in digital music signal restoration field, because of corrupted samples that must be replaced. The subband approach allows for the reconstruction of a long audio data sequence from forward-backward predicted samples. In order to improve prediction performances, neural networks with spline flexible activation function are used as narrow subband nonlinear forward-backward predictors. Previous neural-networks approaches involved a long training process. Due to the small networks needed for each subband and to the spline adaptive activation functions that speed-up the convergence time and improve the generalization performances, the proposed signal recovery scheme works in online (or in continuous learning) mode as a simple nonlinear adaptive filter. Experimental results show the mean square reconstruction error and maximum error obtained with increasing gap length, from 200 to 5000 samples for different musical genres. A subjective performances analysis is also reported. The method gives good results for the reconstruction of over 100 ms of audio signal with low audible effects in overall quality and outperforms the previous approaches.

Acceptable delays in hearing aids and implications for feedback cancellation

The advent of digital hearing aids has made it possible to realize a vast range of advanced signal processing algorithms. Undoubtedly, some candidate algorithms will involve comprehensive throughput delays. This applies, for instance, to all algorithms that are based on the discrete Fourier transform, due to the inherent block processing. The results of a literature study on the potential audible effects of delays in hearing aids will be presented in an outline. The rather restrictive limitations on throughput delay that appear from this study have consequences for many attractive hearing aid applications of digital signal processing. As an example, digital feedback cancellation without additive probe noise is considered. Such a system is based on adaptive identification of the feedback path, found only by means of the excitation provided by the external input signal to the hearing aid. Since the external input signal appears both as reference and disturbance in the adaptive system identification, the estimate of the feedback path becomes erroneous when the external input signal contains significant amounts of autocorrelation. It is shown that the only effective remedy to this problem is to increase the throughput delay of the hearing aid.

“Crying” electrostatics

Japanese physics teachers have developed a novel electrostatics demonstration that uses and “electrophrus,” a neon light, and an amplifier to make changes in potential audible. This paper provides instructions for construction of a simple apparatus, and an explanation of how the audible effects are obtained.

Some effects of orchestra shells

This paper presents room acoustic measurements of the effects of adding or modifying an orchestra shell in several halls. The average effects, at audience seats, of adding an orchestra shell in three large multipurpose halls were small but within predicted ranges. At mid- and high frequencies, partial shells produced intermediate results. However, at lower frequencies more complex effects were observed, because the addition of an orchestra shell modified the grazing incidence seat dip attenuation. These effects depended on the geometry of the shell and on the receiver position in the hall. On-stage measurements of support were increased by approximately 5 dB with the addition of an orchestra shell. Although orchestra shells had much larger effects on-stage, they were also found to produce significant audible effects at audience seats.

Acoustic feedback and other audible artifacts in hearing AIDS.

Acoustic feedback and other audible artifacts in hearing AIDS.

A dynamic absorber and a side‐branch resonator for vibration and noise control

This paper presents two demonstrations. The first one deals with control of vibrations of a motor under unbalance excitation. A dynamic absorber is used to reduce vibrations of the motor. The resonance phenomenon and mode shapes in vibrating systems will be shown. The second system is a finite length duct with an acoustic source (speaker) at one end. A Helmholtz resonator as a side‐branch device is used to reduce the noise radiating from the open‐end of the duct. Audible effects due to acoustic resonances in the duct and side‐branch resonator system will be presented.

The effect of intensity on gap detection in hearing-impaired listeners

Previous investigations of gap detection by hearing-impaired listeners have yielded results that are inconsistent across listeners and studies. The full effect of stimulus intensity and audibility on hearing-impaired listeners’ performance has not been described. This study investigated the effect of intensity on gap detection abilities of normal-hearing listeners and listeners with similar mild to moderate high-frequency hearing impairments. Listeners were required to detect a gap in a high-frequency narrow-band noise over a wide range of intensities above threshold, and to judge the loudness of the signal. Results indicated that at low intensities all listeners showed reduced gap detection ability. As intensity increased, the listeners’ performance improved and stabilized at high sensation levels. At these higher intensities, the performance of hearing-impaired listeners was similar to, but still significantly different from that of normals (mean group difference=1 ms). This difference in listeners’ performance was found when results were compared in sensation level, sound-pressure level, and loudness. Consistent results across eight hearing-impaired listeners suggested that ensuring full audibility of the stimulus yields more consistent performance. These results suggest that temporal resolution ability is affected by both hearing impairment and by stimulus intensity.

Stop consonant recognition and audibility in normal and hearing‐loss subjects

This study examined the effect of spectral cue audibility on the discrimination of CV stop consonants in normal‐hearing and hearing‐impaired adults. Six synthetic speech tokens, each differing only in the initial 40‐ms consonant portion, were presented to subjects in randomized lists. Performance‐intensity functions and relative information transmitted were calculated from the results of a six‐alternative, closed‐set response task, In both normal‐hearing and hearing‐impaired subjects, recognition performance as a function of level differed among the six consonants. The first 40 ms of each CV were analyzed via FFT using an exponential window. The resulting spectral array was passed through a sliding‐filter model of the auditory system to account for the proportional bandwidth filtering properties of the ear. This allowed the spectral data to be displayed in comparison to a subject's pure‐tone thresholds. Differences in the amount of predicted audible spectral speech cues resulted in observable differences in the recognition performance of individual consonants.

Chemistry of Fireworks

During the upcoming Fourth of July holiday, nearly $100 million worth of fireworks will be discharged in the spectacular annual chemical celebration of the Declaration of Independence. Although technical advances of the 19th and 20th centuries have created many new industries and drastically changed most others, the fireworks industry continues to use many materials, formulations, and production methods dating back to the time of the American Revolution and even considerably before. The production of visible and audible effects by the ignition of chemical mixtures traditionally has been treated as an empirical art by fireworks companies, with formulas and methods carefully guarded and handed down unchanged from generation to generation. Only in this century, mainly as the result of defense-related projects, are the scientific roots of the industry being investigated, using modern instrumentation and research techniques. Pyrotechnic mixtures, upon ignition, produce light, color, noise, heat, smoke, and mot...

Subjective sound quality of all-pass networks

In an earlier study [J. Acoust. Soc. Am. 54, 334 (1973)] we reported that the subjective quality of music appeared to be unaffected by processing signals through all-pass phase-shift networks as used in the SQ quadraphonic matrix encoding system. These conclusions were based on the results of a same/different experiment in which the listeners appeared to be operating at a chance level for a two-alternative forced-choice paradigm. They responded with an equal likelihood (50%) of same and different regardless of the nature of the stimulus pairs. Additional experiments have been performed with speech samples using several lists of Harvard PB Sentences. In a same/different experiment, the listeners overwhelmingly judged “same” regardless of conditions. However, in an A-B-X experiment, the listeners favored the “B” choice, the one nearest the time to the unknown. Foil conditions of high-pass filtering, low-pass filtering, and peak-clipping were included to verify the performance of the listeners. Correct responses to these conditions were provided except at near discrimination thresholds. One may therefore conclude that such all-pass networks have no audible effect on subjective quality. In addition, whe presented with a difficult A-B-X discrimination task, a significant response bias results from a preference to the stimulus closest in time to the unknown.

Audio-disc scratch filter

A new method of detecting and removing the audible effects of scratch imperfections on audio discs is described.

The ‘Thunder Effect’ — A Problem of the Sound Film

This article surveys the history of systematic assessment of the operating conditions in photographic sound recording before 1945 and suggests that the work should be resumed in order to relate the old results to more recent insights. Since there is no unique English term to describe the audible effect of image spread in a photographic sound track the descriptive German term “thunder-effect” has been retained.

"Soft limiting" in audio power amplification

A method of instantaneous automatic compression of large signals, called "soft limiting", generates much less harmonic distortion than uncontrolled clipping. If the audible effect of finite-power output (clipping) is prevented, the effect should be the illusion of greater power reserve while reducing manufacturing costs.

Surface Characteristics of Fractured Poly(methyl methacrylate)

A STUDY of fracture phenomena in poly (methyl methacrylate) has been undertaken, which involves the breaking, in tension, of strip samples, each containing a preformed crack which lies in a plane normal to the long axis (Fig. 1). The samples are extended at fixed rates of elongation until rupture ensues, invariably at the site of the initial crack. It appears by visual inspection that the fracture process occurs in two distinct stages. The crack starts to grow fairly slowly at a velocity which is of the order of 0.1 cm./sec., until a critical stage is reached when the velocity suddenly increases to a value of at least 104 cm./sec. It is not yet known what factor is critical in producing the transition. The final high velocity is possibly the theoretical maximum, limited by the velocity of a longitudinal wave in the medium1, but no accurate measurements have yet been made. A sharp characteristic audible effect is associated with the rapid stage of crack growth.

The acoustic design of talks studios and listening rooms

The paper gives the current views of the author and his colleagues in the Engineering Department of the British Broadcasting Corporation on the design and construction of talks studios and listening rooms or control cubicles, which are considered together on account of their similarity with respect to acoustic behaviour. It is shown that a distinctive characteristic is that, because their dimensions are comparable with the wavelength of low-frequency sound, the sound field is characterized by strong simple standing-wave patterns which cannot be eliminated without eliminating the reverberation itself. It is shown also that the audible effects are confined to those associated with simple axial modes and that, by careful adjustment of dimensions, provision of diffusion and the proper distribution of absorbing material, the worst faults can be avoided. The effects of the monaural listening chain are considered as well as the consequent necessity for reduced background noise and reverberation in studios as compared with a normal living-room.Finally, design data for both talks studios and control or listening cubicles are given.