Showing papers in "Canadian Acoustics in 1988"
Journal Article•
TL;DR: The CSA Standard Z107.56 `Procedures for the Measurements of Occupational Noise Exposure' comprises a main body and four Appendices, which deals with the measurement of noise exposure of groups of workers using statistical sampling methods.
Abstract: The CSA Standard Z107.56 `Procedures for the Measurements of Occupational Noise Exposure' comprises a main body and four Appendices. Appendix B deals with the measurement of noise exposure of groups of workers using statistical sampling methods. Some rather complicated mathematical treatments of the data are required. These calculations can be performed very easily using the computer program described in this paper. The program is menu driven and user friendly. It has been offered to CSA for distribution
6 citations
Journal Article•
TL;DR: In this article, the results obtained with the white noise method and the more traditional pure tone analysis were compared and a comparison was given between the results of the white noises and the traditional pure tones analysis.
Abstract: Linear systems analysis with tones, clicks or white noise results essentially in the same information: the impulse response or frequency response of the system. In non-linear systems, such as the auditory system, these three methods provide different results. Furthermore the outcome will be level dependent. Higher order cross correlation with Gaussian wide band noise as input signal provides, in principle, a method to analyze non-linear systems. For that purpose one needs noise with a zero valued second order auto correlation function. Commercially available pseudo-random noise generators do not produce noise with satisfactory properties. Software generated noise with Gaussian amplitude distribution can easily be generated on basis of the uniform distributed random number generator. Using noise with these improved characteristics the authors studied neurons in the auditory midbrain of the grassfrog. Two examples are shown and a comparison is given between the results obtained with the white noise method and the more traditional pure tone analysis
4 citations
Journal Article•
TL;DR: In this article, the authors used the psychophysical method of constant stimuli to discriminate the musical octave with respect to a correctly tuned octave, and found that the discrepancy between the subjective octave and the physical octave was typically in favour of a ''stretched'' subjective OCTave about 20 cents wider than the physical OCTave, when the two tones were separated by silence or by two musically related tones.
Abstract: Discrimination of the musical octave was studied using the psychophysical method of constant stimuli. Stimuli were two successive pure tones whose ratio varied in discrete steps from 100 cents below to 100 cents above the physical octave of 1200 cents. Listeners judged whether each pair was flat or sharp with respect to a correctly tuned octave. Two measures were estimated for each of ten listeners. The first was a measure of sensitivity, the difference limen. The second was the subjective criterion for the octave, or that tuning judged equally likely to be sharp or flat. For two tones in immediate succession the results were in accord with previous investigations: the discrepancy between the subjective octave and the physical octave was typically in favour of a `stretched' subjective octave about 20 cents wider than the physical octave. However, the magnitude of the stretch decreased, and sensitivity of discrimination increased, when the two tones were separated either by silence or by two musically related tones-in this case, the notes of the equal-tempered major triad. The results suggest that the criterion for the subjective octave is influenced by context and by the listener's strategy. Thus, in music, a flexible choice of tuning criteria may be desirable
4 citations
Journal Article•
TL;DR: In this article, the authors evaluate the inportanœ of various cannon parameters associated with suspended ceilings in a realistic but controlled manner, such as ceiling panel STC, return air openings, plenum absorption and plenum barriers.
Abstract: There is very little practical information available on the acoustical performance of suspended ceilings used in an office environnent. It is very difficult to determine the influence of specific elements through a ocnparison of field measurements since there are many unknown conditions that change frcan one site to the next. The purpose of this study was to evaluate the inportanœ of various cannon parameters associated with suspended ceilings in a realistic but controlled manner. Effects of ceiling panel STC, return air openings, plenum absorption, plenum barriers and ceiling sandwich construction were measured.
3 citations
Journal Article•
TL;DR: The results of a comprehensive study on the evaluation of hearing protection devices with respect to the Canadian standard were discussed in this paper, where the authors concluded that the Canadian standards are more realistic in its philosophy than are other standard rating schemes.
Abstract: The results of a comprehensive study on the evaluation of hearing protection devices are discussed with respect to the Canadian standard. Overall the Canadian standard is more realistic in its philosophy than are other standard rating schemes
Journal Article•
TL;DR: In this article, a field study has been conducted in 50 classrooms from 6 primary schools in Montreal in order to identify physical characteristics that would predict speech intelligibility in classrooms, namely the absence of ventilation noise, the enclosure of the rooms by complete partitions and the presence of acoustic tiles on the ceiling.
Abstract: A field study has been conducted in 50 classrooms from 6 primary schools in Montreal in order to identify physical characteristics that would predict speech intelligibility in classrooms. An empirical model founded on the evaluation of the signal-to-noise ratio in dBA and of the reverberation time at 1000 Hz has been used. Three variables have been identified as predictors of an optimal speech intelligibility in classrooms, namely the absence of ventilation noise, the enclosure of the rooms by complete partitions and the presence of acoustic tiles on the ceiling.
Journal Article•
TL;DR: To establish normative values for natural production, jitter and shimmer were measured for nine Canadian English vowels, produced by eight male and eight female speakers in the sentence frame `Please say /hVd/ not /h Vd/.
Abstract: To establish normative values for natural production, jitter (glottal period perturbation) and shimmer (amplitude perturbation) were measured for nine Canadian English vowels, produced by eight male and eight female speakers in the sentence frame `Please say /hVd/ not /hVd/.' The speech signals were digitized at a 20 kHz sampling rate. Following extraction of the vowel, the duration and peak amplitude of each period were measured using a semi-automatic peak-picking procedure with quadratic interpolation. Jitter and shimmer were determined as distance from a two-point linear trend line centered around the current period. Period measures were normalized by dividing this distance by the local mean period duration averaged across three periods; a similar measure was employed for shimmer. For both jitter and shimmer, unexpectedly large differences among speakers were found. The relation between jitter and shimmer within the vowel was also investigated by cross-correlating the signed jitter and shimmer perturbations of individual vowel periods. Significant correlations appeared for less than one quarter of the vowel tokens
Journal Article•
TL;DR: The Canadian Acoustical Association encompasses a wide spectrum of research interests, all linked by the common factor, acoustics, but perhaps not all soundly linked! The activities of the CAA parallel in many ways those of its big brother/sister the ACoustical Society of America, but compared to the ASA one area has been largely (but not totally) unrepresented in CAA, namely auditory physiology as discussed by the authors.
Abstract: The Canadian Acoustical Association encompasses a wide spectrum of research interests, all linked by the common factor, acoustics, (but perhaps not all soundly linked!) The activities of the CAA parallel in many ways those of its big brother/sister the Acoustical Society of America, but compared to the ASA one area has been largely (but not totally) unrepresented in the CAA, namely auditory physiology. However, recent years have seen the maturation of a number of physiological research groups throughout Canada. One of the main functions of the CAA is to promote interactions between groups or individuals with similar research interests, and the vehicle for such communication is this journal, Canadian Acoustics. To assist the spread of information I have agreed to the request of the editor-in-chief to provide a summary the research in auditory physiology being carried out in laboratories in Toronto, at the Hospital for Sick Children, and at the University.