Joos Vos

Annoyance caused by simultaneous impulse, road‐traffic, and aircraft sounds: A quantitative model

In this study, total annoyance caused by different simultaneous environmental sounds is investigated. In spite of a number of puzzling data in the literature, it is fairly well established that in combinations in which the annoyance of one source is considerably higher than that of another source, total annoyance is equal to the maximum annoyance of the separate sources. For combinations in which both sounds are about equally annoying, total annoyance seems to be higher than the maximum source-specific annoyance. The available data, however, are too rough to model total annoyance in these conditions. The present laboratory studies were therefore designed to explore further possible procedures to quantify total annoyance. Subjects rated the (total) annoyance caused by various combinations of impulse, road-traffic, and aircraft sounds. The results support a simple model which predicts the overall or total rating sound level L(t) for combinations of several types of sounds. Here, L(t) is numerically equal to the A-weighted equivalent sound level L(eq) of road-traffic sound with the same annoyance as caused by the combination of sounds. In the model, the sound exposure caused by the impulse and/or aircraft sounds is first expressed in the L(eq) of equally annoying road-traffic sound. With the help of source-specific dose-effect relationships, this is achieved by adding level-dependent penalties to the L(eq) of the respective sources. Weighted summation of the corrected L(eq)s of the various sources then results in L(t). An optimal overall fit of the data from two separate experiments was obtained when the weighted summation of the corrected L(eq)s was performed with the parameter k in k log(sigma 10(corrected L(eq) of source j)/k) set to 15. The standard deviation of the differences between the experimental results and the model predictions with k = 15 was equivalent to the small change in annoyance produced by a 1.5-dB shift in the L(eq) of road-traffic sound. Adoption of k = 15 implies that after correction, two equal L(eq)s yield a total rating sound level which is 4.5 dB higher than each single-source corrected L(eq).

Thresholds for discrimination between pure and tempered intervals: The relevance of nearly coinciding harmonics

Thresholds for discrimination between pure and tempered musical intervals consisting of simultaneous complex tones (fundamental frequencies f1 and f2) were investigated. For these tones the main clue for the discrimination of pure intervals (f1:f2 = p:q; p and q small integers) from moderately tempered intervals (f1:f2 approximately p:q) is absence versus presence of beats. The strength of the beats (level difference between envelope maximum and minimum or level-variation depth D) was manipulated by introduction of differences in level (delta L) between the two tones. In each of three experiments the discrimination thresholds (DTs) were determined for 13 intervals with different values for p and/or q. Experiment 1 showed that there is a simple relation between frequency-ratio complexity and discriminability: DTs gradually increased (smaller values of delta L) with increasing p + q. Experiment 2, in which tones with harmonics of equal amplitude were used, indicated that level of the interfering harmonics was not responsible for the relation between DT and p + q. Yet, Experiment 3, in which the spectral content of the tones was varied, clearly showed that for all intervals DT had been determined by the interference between nearly coinciding harmonics. Detailed analysis of the results revealed that the relation between DT and ratio complexity might have been the result of masking.

Subjective acceptability of various regular twelve-tone tuning systems in two-part musical fragments.

Musically trained subjects rated the overall acceptability of the performance of two-part musical fragments. With the help of a computer these fragments were produced with intonations according to various regular 12-tone tuning systems: Pythagorean tuning (tempering T of the fifths equal to 0.0 cent), equal temperament (T = -2.0 cents), Silbermann (T = -3.9 cents), mean-tone (T = -5.4 cents), and Salinas tuning (T = -7.2 cents). In experiment 1, two systems in which T = 2.0 or T = -10.0 cents were also included. In both the lower and the higher parts of the fragments we used complex tones with a spectral-envelope slope of -6 dB/oct. Mean acceptability ratings were about the same for -5.4 less than or equal to T less than or equal to 0.0 cent, whereas for T greater than 0.0 and T less than -5.4 cents the ratings strongly decreased. This effect of tuning system was also found when acceptability was determined by means of the method of paired comparisons. The specific effect of tuning system was not affected by the tempo of the fragments. The perception of beats in the harmonic intervals was manipulated in experiment 2 by varying the spectral content of the tones. The condition in which the interference of the nearly coinciding harmonics was canceled resulted in higher acceptability. The effect of tuning system was the same as in experiment 1. In both experiments overall acceptability could be accurately predicted from a linear combination of the purity ratings of the isolated harmonic fifths and major thirds. It is not precluded, however, that for T greater than 0.0 and T less than -5.4 cents, the subjects based their acceptability ratings partly on the subjective purity of the melodic intervals.

Spectral effects in the perception of pure and tempered intervals: Discrimination and beats

Thresholds for discrimination between pure and tempered musical intervals consisting of simultaneous complex tones have been investigated previously (Vos. 1982). The aim of the present research was to answer three questions: (1) To what extent are these thresholds determined by the interference of just-noncoinciding harmonics? (2) Is the beat frequency of the first pair of these adjacent harmonics equal to the perceived beat frequency of the tempered intervals? (3) Are differences in discriminability at threshold representative of differences between the perceived strength of beats in supraliminal conditions? In the first three experiments, the answer to the first question was sought by investigating the effect of spectral content of the tones on the (Uscrimination thresholds (DTs) for the fifth (Experiment 1) and the major third (Experiments 2 and 3). The results showed that, for moderately tempered fifths, DTs are determined mainly by the interference of the first pair of adjacent harmonics. For major thirds, however, the data suggest that the interference of other harmonics plays a role as well. In Experiment 4, attempts were made to answer the second and third questions: In supraliminal conditions, both the dominantly perceived beat frequency and the perceived beat strength were determined for various spectral conditions and degrees of tempering. For both the fifth and the major third and for all spectral conditions, the dominantly perceived beat frequency was in most cases equal to the frequency difference of the first pair of adjacent harmonics. Comparison of the DTs and the perceived strength of the beats for corresponding spectral conditions revealed that, especially for the fifth, perceived strength of beats and sensitivity to moderately tempered intervals are highly correlated.

Effect on numerosity judgment of grouping of tones by auditory channels

Previous research suggests that numerosity judgments for sequences of tones improve when the sequence is structured such that equal and small groups of tones alternate between the ears. The present. study systematically investigates the effects of the structure of tone sequences on number judgment. Tone frequency is chosen as the grouping principle instead of spatial location. In the first experiment, sequences with equal groups of 2, 3, 4, 5, 6, or 7 tones (groups alternating between 800 and 1, 250 Hz) were compared with monotonous sequences. At a slow repetition rate of the tones (280 msec onset to onset), grouping the sequence deteriorated the numerosity judgment. At II fast repetition rate of the tones (100 msec onset to onset) grouping improved numerosity judgment, but only if the group size did not exceed 4 to 5 tones. In the second experiment, the equality of group size in the sequence as a necessary condition for the improvement was investigated. It was found that tone sequences comprised of equal groups were judged more accurately in number than sequences comprised of unequal groups. These results seem to give support for the existence of an auditory subitizing process. The results of this study are also compared with the results of studies in which sequences of tones, alternating one by om! between locations or frequencies, had to be judged in number.

A- and C-weighted sound levels as predictors of the annoyance caused by shooting sounds, for various facade attenuation types

In a previous study on the annoyance caused by a great variety of shooting sounds [J. Acoust. Soc. Am. 109, 244-253 (2001)], it was shown that the annoyance, as rated indoors with the windows closed, could be adequately predicted from the outdoor A-weighted and C-weighted sound-exposure levels [ASEL (L(AE)) and CSEL (L(CE))] of the impulse sounds. The explained variance in the mean ratings by (outdoor) ASEL was significantly increased by adding the product (L(CE) - L(AE))(L(AE)) as a second variable. In the present study it was investigated to which extent the additional contribution of the second predictor is also relevant for façade attenuation types with lower and higher degrees of sound isolation than applied previously. Twenty subjects rated the indoor annoyance caused by 11 different impulse types produced by firearms ranging in caliber from 7.62 to 155 mm, at various levels and for five façade attenuation conditions. The effect of façade attenuation on the ratings was large and consistent. In all conditions, an optimal prediction of the annoyance was obtained with outdoor ASEL as the first, and (L(CE) - L(AE))(L(AE)) as the second predictor. The benefit of the second predictor, expressed as the increase in the explained variance, ranged from 2.5 to 55 percent points, and strongly increased with the degree of façade attenuation. It was concluded that for the determination of the rating sound level, the acoustic parameters ASEL and CSEL are very powerful. In addition, the results showed that for the whole set of impulses included, the annoyance could also be predicted very well by the weighted sum of indoor ASEL and the product (L(CE) - L(AE))(L(AE)).

On the level‐dependent penalty for impulse sound

At relatively low A-weighted equivalent levels (Leq), road-traffic sounds are rated to be less annoying than impulse sounds. The differences, however, decrease with increasing Leq of the sounds, which indicates that the penalty for impulse sound seems to be level dependent. It was questioned whether the decrease of the penalty with increasing Leq might, at least partly, have been a consequence of the use of the ten-point rating scale. In experiments 1 and 2, the relevance of the level-dependent correction was therefore studied further by using the method of adjustment. The mean results again showed that, at least for gunfire sounds (small arms), the penalty is level dependent. The drawing of firm conclusions, however, was hampered by a relatively large bias in the adjustments. In addition, the overall size of the penalty was lower than obtained in previous rating experiments. The question about the relevance of the level-dependent penalty was reopened in experiment 3 by applying the method of paired comparison. The results confirm the previous findings obtained with the rating experiments: For gunfire sounds at relatively low indoor Leq values, a penalty of about 10 dB is required, and a penalty lower than 5 dB can be applied only in conditions with rather high sound exposure. The results further showed that especially at indoor Leq values higher than about 45 to 50 dB(A), application of a negative penalty may become relevant for specific sounds such as those produced by the 0.50-in. machine gun. Consequently, acoustic measures from which to predict the value of the penalty are highly needed.

Leq as a measure of annoyance caused by gunfire consisting of impulses with various proportions of higher and lower sound levels

As a method of rating sounds with respect to the expected community response, ISO(1971). ISO R 1996, ‘‘Assessment of noise with respect to community response’’ (International organization for Standarization, Switzerland), recommends the measurement of the A‐weighted equivalent sound level Leq. The usefulness of Leq for road‐traffic sounds has been demonstrated in various studies. For impulse sounds, however, research into the adequacy of Leq has been very limited. The present laboratory study provides a further test of the adequacy of Leq as a descriptor of annoyance. In one condition, all impulse sounds had the same level, whereas in the other eight conditions the levels of the impulses could differ either by 6 or by 12 dB. The proportions of the impulses with high or low sound levels were 90% vs 10%, 75% vs 25%, and vice versa. Sixteen subjects compared the annoyance caused by the impulse sounds (G) with the annoyance due to road‐traffic sounds (T). They adjusted the level of either T or G in such a way...

The effect of fundamental frequency on the discriminability between pure and tempered fifths and major thirds

Thresholds were determined for discrimination between pure and tempered musical intervals (DTs) consisting of simultaneous complex tones. Tempered intervals are characterized by small frequency differences between those harmonics that coincide in pure intervals, Interference of these nearly coinciding harmonics gives rise to the perception of beats. Two parameters of beats were varied independently: (l) beat frequency and (2) depth of level variation (temporal envelope) as a measure of DT. DTs were determined for musical fifths and major thirds at a tone duration of 0.5 sec, The geometric mean of the fundamental frequency of the tones was varied in octave steps from 92.5 to 740 Hz, The beat frequency of the intervals was varied within a range of 2 to 64 Hz. The major result of our experiment was that, for a frequency range comprising 3 to 4 octaves, DTs do not depend on the frequency of the fundamentals, provided that the DTs are ordered according to beat frequency, When tempering (T) is expressed in cents and only those conditions are considered in which the degree of T corresponds to that found in the relevant tuning systems, it can be concluded that perceptual differences between tempered and pure fifths are increasingly irrelevant for tones lower than about middle C (262 Hz). Tempered major thirds, even those in a compromise tuning system such as that proposed by Silbermann (T=6 cents), can be discriminated from pure major thirds for all fundamental frequencies that are relevant in musical composition.

Attention-switching and grouping in counting interaurally presented clicks ☆

Abstract The present study tests the hypothesis that attention-switching is time-consuming and performance-limiting. Analysis of previous research on counting interaurally presented clicks shows that estimates of ‘switch-times’ can be made, based on the data of Guzy and Axelrod (1972). In the earlier click-counting studies, however, the number of clicks to be counted and the number of physical switches between the ears were confouned. Hence the number of clicks, number of physical switches and interval between clicks were independently varied. The results showed that (a) counting performance did not decrease monotonically with increasing number of switches in the click sequence; (b) no difference in counting performance could be found between the monaural and completely alternating interaural presentation; (c) when the number of switches in the sequence was small and equal groups of clicks alternated between ears, performance dramatically improved. With these kinds of sequences, subjects presumably do not count the clicks one at a time, but subitize a group of clicks.