Directional sound field decay analysis in coupled spaces

The paper deals with the differences between the energy created by four different pulsed sound sources, ie a sound gun, a start gun, a toy gun, and a hunting gun. A knowledge of the differences between the maximum energy and the minimum energy, or the signal-noise ratio, is necessary to correctly calculate the frequency dependence of reverberation time. It has been established by investigations that the maximum energy excited by the sound gun is within the frequency range of 250 to 2000 Hz. It decreases by about 28 dB at the low frequencies. The character of change in the energy created by the hunting gun differs from that of the sound gun. There is no change in the maximum energy within the frequency range of 63–100 Hz, whereas afterwards it increases with the increase in frequency but only to the limit of 2000 Hz. In the frequency range of 63–500 Hz, the energy excited by the hunting gun is lower by 15–30 dB than that of the sound gun. As frequency increases the difference is reduced and amounts to 5–10 dB. The maximum energy of the start gun is lower by 4–5 dB than that of the hunting gun in the frequency range of up to 1000 Hz, while afterwards the difference is insignificant. In the frequency range of 125–250 Hz, the maximum energy generated by the sound gun exceeds that generated by the hunting gun by 20 dB, that by the start gun by 25 dB, and that by the toy gun—by as much as 35 dB. The maximum energy emitted by it occupies a wide frequency range of 250 to 2000 Hz. Thus, the sound gun has an advantage over the other three sound sources from the point of view of maximum energy. Up until 500 Hz the character of change in the direct sound energy is similar for all types of sources. The maximum energy of direct sound is also created by the sound gun and it increases along with frequency, the maximum values being reached at 500 Hz and 1000 Hz. The maximum energy of the hunting gun in the frequency range of 125—500 Hz is lower by about 20 dB than that of the sound gun, while the maximum energy of the toy gun is lower by about 25 dB. The maximum of the direct sound energy generated by the hunting gun, the start gun and the toy gun is found at high frequencies, ie at 1000 Hz and 2000 Hz, while the sound gun generates the maximum energy at 500 Hz and 1000 Hz. Thus, the best results are obtained when the energy is emitted by the sound gun. When the sound field is generated by the sound gun, the difference between the maximum energy and the noise level is about 35 dB at 63 Hz, while the use of the hunting gun reduces the difference to about 20–22 dB. The start gun emits only small quantities of low frequencies and is not suitable for room's acoustical analysis at 63 Hz. At the frequency of 80 Hz, the difference between the maximum energy and the noise level makes up about 50 dB, when the sound field is generated by the sound gun, and about 27 dB, when it is generated by the hunting gun. When the start gun is used, the difference between the maximum signal and the noise level is as small as 20 dB, which is not sufficient to make a reverberation time analysis correctly. At the frequency of 100 Hz, the difference of about 55 dB between the maximum energy and the noise level is only achieved by the sound gun. The hunting gun, the start gun and the toy gun create the decrease of about 25 dB, which is not sufficient for the calculation of the reverberation time. At the frequency of 125 Hz, a sufficiently large difference in the sound field decay amounting to about 40 dB is created by the sound gun, the hunting gun and the start gun, though the character of the sound field curve decay of the latter is different from the former two. At 250 Hz, the sound gun produces a field decay difference of almost 60 dB, the hunting gun almost 50 dB, the start gun almost 40 dB, and the toy gun about 45 dB. At 500 Hz, the sound field decay is sufficient when any of the four sound sources is used. The energy difference created by the sound gun is as large as 70 dB, by the hunting gun 50 dB, by the start gun 52 dB, and by the toy gun 48 dB. Such energy differences are sufficient for the analysis of acoustic indicators. At the high frequencies of 1000 to 4000 Hz, all the four sound sources used, even the toy gun, produce a good difference of the sound field decay and in all cases it is possible to analyse the reverberation process at varied intervals of the sound level decay.

Download Full-text

Directional sound field decay analysis in performance spaces

Building Acoustics ◽

10.1177/1351010x20984622 ◽

2021 ◽

pp. 1351010X2098462

Author(s):

Marco Berzborn ◽

Michael Vorländer

Keyword(s):

Temporal Evolution ◽

Sound Field ◽

General Purpose ◽

Room Acoustics ◽

Complex Geometries ◽

Sound Fields ◽

Temporal Features ◽

Spatio Temporal ◽

Field Decay ◽

Late Part

The analysis of the spatio-temporal features of sound fields is of great interest in the field of room acoustics, as they inevitably contribute to a listeners impression of the room. The perceived spaciousness is linked to lateral sound incidence during the early and late part of the impulse response which largely depends on the geometry of the room. In complex geometries, particularly in rooms with reverberation reservoirs or coupled spaces, the reverberation process might show distinct spatio-temporal characteristics. In the present study, we apply the analysis of directional energy decay curves based on the decomposition of the sound field into a plane wave basis, previously proposed for reverberation room characterization, to general purpose performance spaces. A simulation study of a concert hall and two churches is presented uncovering anisotropic sound field decays in two cases and highlighting implications for the resulting temporal evolution of the sound field diffuseness.

Download Full-text

Directional Sound Field Decay Analysis in Coupled Spaces

10.26226/morressier.606f15dd30a2e980041f24c3 ◽

2021 ◽

Author(s):

Marco Berzborn ◽

Jamilla Balint ◽

Michael Vorlaender

Keyword(s):

Sound Field ◽

Field Decay

Download Full-text

THE FEATURES OF CINEMA HALL ACOUSTICS UPON INSTALLATION OF THE DOLBY SOUND RECORDING SYSTEM/KINO TEATRO AKUSTIKOS YPATUMAI, ĮRENGUS “DOLBY” ĮGARSINIMO SISTEMĄ

Journal of Civil Engineering and Management ◽

10.3846/13921525.1999.10531481 ◽

1999 ◽

Vol 5 (5) ◽

pp. 312-317

Author(s):

Vytautas Stauskis

Keyword(s):

Sound Field ◽

Recording System ◽

Subjective Perception ◽

Reverberation Time ◽

Sound Recording ◽

Energy Increase ◽

Energy Value ◽

Maximal Energy ◽

Upper Limit ◽

Field Decay

Investigations conducted in a cinema hall have shown that the character of the sound field decay in all rows of the main floor is uniform. The character of the sound field decay in the balcony is similar to that on the main floor. The maximal decay energy in the balcony is lower by about 2 dB compared to that on the main floor. After the reconstruction of the hall, the energy decay of a similar character was found both on the main floor and in the balcony. The decay of energy is much faster because the sound absorption of the entire hall has increased. The maximal energy values, however, are higher in the balcony and under it compared to the main floor. After the reconstruction the overall hall absorption has increased by about 200–300 m2 both on the main floor and in the balcony. Consequently, the reconstruction should have resulted in the decrease of the maximal energy in both areas. Actually, the maximal energy value is higher in the balcony. At the frequency 63 Hz, the maximal energy value in the balcony after the reconstruction, ie after the increase in the overall absorption, is by 10 dB higher than that before reconstruction when the absorption was smaller. One would expect a reverse. A similar effect is observed in the rows under the balcony. At 1000 Hz and 2000 Hz the energy increase is 4–5 dB and it starts after 50 ms. At 4000 Hz a maximal energy increase of 7–8 dB is reached after 100 ms. Before the reconstruction the early reverberation time T10 markedly exceeded the permissible upper limit in all rows of the hall, and particularly at the end of the hall and in the balcony at the frequency from 63 to 500 Hz. As the sound field decay was approximated by larger level intervals, eg from 0 to −30 dB, still larger reverberation time values were obtained. After the reconstruction the early reverberation time in all rows of the main hall and the balcony does not exceed the permissible upper limit. It is only in the frequency range of 250–1000 Hz that the reverberation time values are below the lower limit. In this case, the listener's subjective perception will be of a weaker sound, which is strongly preferable, since the sound is too strong in Lithuanian cinema halls where the Dolby sound-recording system has been installed.

Download Full-text

Decay of Non-Diffuse Sound Fields in a Room

MATEC Web of Conferences ◽

10.1051/matecconf/202032000006 ◽

2020 ◽

Vol 320 ◽

pp. 00006

Author(s):

Alena Novoselova ◽

Nikolay Kanev

Keyword(s):

Sound Source ◽

Relative Position ◽

Sound Field ◽

Strong Anisotropy ◽

Sound Fields ◽

The Third ◽

Field Diffusion ◽

Absorbing Material ◽

Field Decay ◽

Exponential Power

The paper presents the results of a study of a non-diffuse sound field decay in a room. In a laboratory experiment, a model of a room in the form of a rectangular parallelepiped with a size of 0.7 x 0.4 x 0.4 m is used. Two non-parallel walls are coated with sound absorbing material. Sound scattering elements can be placed on the third wall which is perpendicular to the absorbing ones, which allows to change the field diffusion degree. The sound field in such a room has a strong anisotropy, its energy decays according to the exponential-power law. Sound decay curves were measured at various positions of the sound source and microphone at frequencies of 4 kHz. The decay curves are compared, their dependence on the relative position of the sound source and microphone is analyzed.

Download Full-text

PULSE LENGTH DEPENDENCE ON THE DECAY OF THE INTEGRATED PULSE ENERGY/INTEGRUOTO IMPULSO ENERGIJOS SLOPIMO PRIKLAUSOMYBĖ NUO SKIRTINGŲ IMPULSO ILGIŲ

Journal of Civil Engineering and Management ◽

10.3846/13921525.2000.10531588 ◽

2000 ◽

Vol 6 (3) ◽

pp. 206-212

Author(s):

Vytautas Stauskis

Keyword(s):

Background Noise ◽

Pulse Length ◽

Low Frequency ◽

Sound Field ◽

Maximum Energy ◽

Energy Decay ◽

Field Energy ◽

Time Interval ◽

Field Decay ◽

The Right

The paper deals with the influence of the pulse length on the decay of the sound field energy. Six pulse lengths— 2000, 2500, 3000, 3500, 4000 and 4500 ms—were selected for investigations. Investigations show that a 2500 ms pulse is too short to correctly assess the background noise time interval. Such pulse length is not suitable for experiments. 3000 ms is the right length, while 3500 ms may be too long, resulting in errors of measurement results. When the pulse length increases to 4000 ms, the decay starting from 2000 ms is different from the pulse length 2500 ms and 3000 ms. Background noise starts from 2300 ms for these pulses, while for a 4000 ms pulse it starts from 3200 to 3300 ms. The length of 4500 ms is completely not suitable for investigations because the background noise zone starts very early, ie at 1800 ms, while for a short 2500 ms pulse it starts much later, after 2300 ms. While investigating energy decay, it is important to determine the maximum decay. At 63 Hz the sound field decay is almost uniform till— 18 dB. Later the decay character is different. The decay of the longest (4500 ms) and the shortest (2500 ms) pulse after— 18 dB is very steep and reaches—30 dB. However, the decay is influenced by the background noise. Thus the shortest and the longest pulses are not suitable for the lowest frequencies. The greatest energy decay is characteristic of the 3000 ms pulse. After 1700 ms energy decreases to—30 dB. Thus at this frequency one may measure the echoing time while approximating decay from 0 to—20 dB. As the frequency increases, the results change. At 100 Hz the energy decays by— 35–37 dB at pulse lengths of 2500 ms and 4000 ms. The greatest decay of— 42 dB is produced by the longest pulse 4500 ms though this arouses certain doubts. Then the echoing time may be measured from 0 to— 30 dB. At 125 octave frequency the smallest maximum decay of— 40 dB is observed with the shortest pulse (2500 ms), while the largest one— 50 dB is produced by the longest pulse (4500 ms). Thus standard echoing time may be measured for this frequency. In the frequency range of 250–2000 Hz, the maximum energy decay is sufficient and amounts to— 50–60 dB. At 4000 Hz the final part of decay is strongly dependent on the pulse length although, as the decay is about— 55 dB in all cases, the standard echoing time may be measured correctly. Pulse length is important only for the calculation of the low-frequency echoing time. At 63–100 Hz the best maximum decay is seen with the pulse 3000 ms long, while at 125 Hz and over the best pulse lengths are from 3000 to 4000 ms. When the hall contains audience and tapestries are on the walls, the energy decay is almost uniform at the pulse lengths of 2000 to 2800 ms. In this case a better decay is obtained with the longest pulse of 2800 ms.

Download Full-text

Decay of Temporary Threshold Shift in Noise

Journal of Speech and Hearing Research ◽

10.1044/jshr.1602.267 ◽

1973 ◽

Vol 16 (2) ◽

pp. 267-270 ◽

Cited By ~ 5

Author(s):

John H. Mills ◽

Seija A. Talo ◽

Gloria S. Gordon

Keyword(s):

Sound Field ◽

Threshold Shift ◽

Temporary Threshold Shift ◽

Octave Band ◽

Band Noise ◽

Lower Asymptote

Groups of monaural chinchillas trained in behavioral audiometry were exposed in a diffuse sound field to an octave-band noise centered at 4.0 k Hz. The growth of temporary threshold shift (TTS) at 5.7 k Hz from zero to an asymptote (TTS ∞ ) required about 24 hours, and the growth of TTS at 5.7 k Hz from an asymptote to a higher asymptote, about 12–24 hours. TTS ∞ can be described by the equation TTS ∞ = 1.6(SPL-A) where A = 47. These results are consistent with those previously reported in this journal by Carder and Miller and Mills and Talo. Whereas the decay of TTS ∞ to zero required about three days, the decay of TTS ∞ to a lower TTS ∞ required about three to seven days. The decay of TTS ∞ in noise, therefore, appears to require slightly more time than the decay of TTS ∞ in the quiet. However, for a given level of noise, the magnitude of TTS ∞ is the same regardless of whether the TTS asymptote is approached from zero, from a lower asymptote, or from a higher asymptote.

Download Full-text

Modified Earpieces and CROS for High Frequency Hearing Losses

Journal of Speech and Hearing Research ◽

10.1044/jshr.1101.204 ◽

1968 ◽

Vol 11 (1) ◽

pp. 204-218 ◽

Cited By ~ 9

Author(s):

Elizabeth Dodds ◽

Earl Harford

Keyword(s):

Hearing Loss ◽

Hearing Aids ◽

High Frequency ◽

Hearing Aid ◽

Sound Field ◽

Intensity Level ◽

Test Results ◽

High Frequency Hearing Loss ◽

Increased Sensitivity ◽

Difficult Cases

Persons with a high frequency hearing loss are difficult cases for whom to find suitable amplification. We have experienced some success with this problem in our Hearing Clinics using a specially designed earmold with a hearing aid. Thirty-five cases with high frequency hearing losses were selected from our clinical files for analysis of test results using standard, vented, and open earpieces. A statistical analysis of test results revealed that PB scores in sound field, using an average conversational intensity level (70 dB SPL), were enhanced when utilizing any one of the three earmolds. This result was due undoubtedly to increased sensitivity provided by the hearing aid. Only the open earmold used with a CROS hearing aid resulted in a significant improvement in discrimination when compared with the group’s unaided PB score under earphones or when comparing inter-earmold scores. These findings suggest that the inclusion of the open earmold with a CROS aid in the audiologist’s armamentarium should increase his flexibility in selecting hearing aids for persons with a high frequency hearing loss.

Download Full-text