Investigations on the balloon as an impulse source

Pätynen, Jukka; Katz, Brian F. G.; Lokki, Tapio

doi:10.1121/1.3518780

Cited by 40 publications

(23 citation statements)

References 19 publications

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“…Consequently, neither source complied with ISO requirements in the low-frequency range, while they satisfy the requirements in the high frequency range. In particular, Patynen et al 11 confirmed, as observed by Griesinger, 9 that the directivity pattern of a popped balloon is influenced by the pin-prick point. A low-frequency energy peak occurs in that direction while a high-frequency peak occurs in the opposite direction.…”

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Optimizing stepwise rotation of dodecahedron sound source to improve the accuracy of room acoustic measures

Martellotta

2013

The Journal of the Acoustical Society of America

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Dodecahedron sound sources are widely used for acoustical measurement purposes as they produce a good approximation of omnidirectional radiation. Evidence shows that such an assumption is acceptable only in the low-frequency range (namely below 1 kHz), while at higher frequencies sound radiation is far from being uniform. In order to improve the accuracy of acoustical measurements obtained from dodecahedron sources, international standard ISO 3382 suggests an averaging of results after a source rotation. This paper investigates the effects of such rotations, both in terms of variations in acoustical parameters and spatial distribution of sound reflections. Taking advantage of a spherical microphone array, the different reflection patterns were mapped as a function of source rotation, showing that some reflections may be considerably attenuated for different aiming directions. This paper investigates the concept of averaging results while changing rotation angles and the minimum number of rotations required to improve the accuracy of the average value. Results show that averages of three measurements carried out at 30° angular steps are closer to actual values and show much less fluctuation. In addition, an averaging of the directional intensity components of the selected responses stabilizes the spatial distribution of the reflections.

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“…8,9 So, sound sources like the "clapper" 10 or the classic balloons 11 have been carefully characterized both in terms of spectrum and directivity. In the first case, directional fluctuations of about 3 dB appeared in the low frequency range, increasing to 5 dB above 1 kHz.…”

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confidence: 99%

Optimizing stepwise rotation of dodecahedron sound source to improve the accuracy of room acoustic measures

Martellotta

2013

The Journal of the Acoustical Society of America

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“…28 Small differences can be detected between different excitation techniques in the measurement of reverberation time, 29 and these differences are mainly encountered at the lowest frequencies for a balloon-pop. 30 The average occupied reverberation time, from the 500 Hz to 2 kHz octave bands, and over four sourcemicrophone positions, RT mean,500-2 kHz , was obtained for each occupied classroom.…”

Section: B Measurement Of the Acoustical Parameters In The Classroomsmentioning

confidence: 99%

Investigations into vocal doses and parameters pertaining to primary school teachers in classrooms

Bottalico

Astolfi

2012

The Journal of the Acoustical Society of America

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Investigations into vocal doses and parameters were carried out on 40 primary school teachers (36 females and 4 males) in six schools in Italy, divided into two groups of three, A and B, on the basis of the type of building and the mid-frequency reverberation time in the classrooms, which was 1.13 and 0.79 s, respectively. A total of 73 working-day samples were collected (66 for females and 7 for males), from which 54 traditional lessons were analyzed separately. The average value over the working days of the mean sound pressure level of the voiced speech at 1 m from the teacher's mouth was 62.1 dB for the females and 57.7 dB for the males, while the voicing time percentage was 25.9 and 25.1 %, respectively. Even though the vocal doses and parameters did not differ for the two school groups, the differences in the subjective scores were significant, with enhanced scores in group B. A 0.72 dB increase in speech level per 1 dB increase in background noise level, L(A90), was found during traditional lessons, as well as an increase in the mean value of the fundamental frequency with an increase in L(A90), at a rate of 1.0 Hz/dB.

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“…Recent studies [11] analysed the properties of balloons and revealed that theya re, in general, unsatisfactory sound sources. Our owne xperiments, presently unpublished, reveal that industrial-grade firecrackers provide very good omnidirectionality,repeatability and areasonably flat spectrum (unchanging with direction and distance, and hence easily perfectly flattened in post-processing).…”

Section: Test Signal and Sound Sourcementioning

confidence: 99%

3D Sound Characterisation in Theatres Employing Microphone Arrays

Farina¹,

Tronchin²

2013

Acta Acustica united with Acustica

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SummaryThe analysis of the sound field's3Dproperties has been strongly improvedinrecent years, after spatial properties of sound propagation have been acknowledged to be important during the design or correction of theatres and auditoria. Besides, ap roper assessment of spatial accuracyi sr equested for 3D sound reproduction systems, initially designed for acoustical virtual reality and nowalso employed in the entertainment/cinema industry (Immsound, Auro-3D, NHK 22.2). Often only monoaural or binaural measurements are performed by means of omni-directional microphones and dummy heads, although international standards likeISO 3382/1:2009 also define some "truly spatial" parameters such as JLFand JLFC. The twolatter parameters are derivedfrom measurements made with apressure velocity (p/v)microphone, butthis is still a2-channel measurement. 3D Impulse Responses (4-channel B-format)h avef or manyy ears been measured and employed for sound reproduction. Recently,higher-order 3D Impulse Responses have been measurable thanks to the availability of compact microphone arrays employing amuch larger number of transducers. In this paper,two procedures for measuring and analysing the complete spatial sound information are presented, which are aimed at creating easy-to-understand images and videos showing the direction-of-arrivalofthe room reflections. The description of these techniques is emphasised. Furthermore, results are illustrated of experiments conducted with the novelm ethodologies in different rooms, including some ancient theatres.

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Investigations on the balloon as an impulse source

Cited by 40 publications

References 19 publications

Optimizing stepwise rotation of dodecahedron sound source to improve the accuracy of room acoustic measures

Optimizing stepwise rotation of dodecahedron sound source to improve the accuracy of room acoustic measures

Investigations into vocal doses and parameters pertaining to primary school teachers in classrooms

3D Sound Characterisation in Theatres Employing Microphone Arrays

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