DE1272993B - Arrangement for the controllable increase of the reverberation time of a listening room - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int CL:

H04b

German class: 21 a2 - 16/02

Number: 1272 993

File number: P 12 72 993.0-31 (C 33578)

Filing date: August 5, 1964

Opening day: July 18, 1968

The invention relates to an arrangement for controllably increasing the reverberation time of an auditorium without any structural change in space.

The term “lecture hall” can also refer to rooms that are open above, in particular amphitheater-like Buildings to be included. One of the most important parameters of a lecture hall is the reverberation time as Function of the frequency. In concert halls in particular, this function is essential Extent influences acoustic properties, ίο which in music as »warmth«, »physical Sound ”,“ full tone ”and“ transparency ”can be described. The reverberation time as a function of Frequency is primarily determined by the dimensions of a lecture hall, and secondarily also by the Surface quality of the boundary walls determined. In terms of dimensions, a lecture hall is made economic reasons generally designed in such a way that with the smallest possible enclosed space a maximum number of listeners can be accommodated, provided the necessary air supply is ensured. Structural changes to the room in order to achieve a cheaper one The course of the reverberation time as a function of the frequency are associated with very high costs, which can only be used in the rarest of cases. It is also often necessary to already have one To adapt lecture halls to a larger number of listeners. In this case it would be favorable to a previous one Maintain the reverberation time, such a significant structural room change is required that this differed little in terms of cost from a new building. Furthermore, the course of the Reverberation time as a function of frequency due to structural changes in the room in the rarest Adapt cases with sufficient accuracy of a predetermined target function, especially under Taking into account the fact that this nominal function in the transmission of speech or different Types of music (classical music, romantic music, jazz music) or when changing Audience shows a very different optimal course.

The purpose of the present invention is to provide an arrangement for controllable Increase in the reverberation time of a lecture hall, which compared to structural changes in the room requires much less effort and, moreover, an adaptation of the course of the Reverberation time as a function of frequency to various setpoint functions recognized as optimal enables.

Arrangement for controllable increase
the reverberation time of a lecture hall

Applicant:

Minister of Technology, London

Representative:

Dr.-Ing. H. Fincke, Dipl.-Ing. H. Bohr
and Dipl.-Ing. S. Staeger, patent attorneys,
8000 Munich 5, Müllerstr. 31

Named as inventor:

Peter Hubert Parkin, Garston, Watford,

Hertfordshire (UK)

Claimed priority:

Great Britain January 24, 1964 (3277)

This is achieved essentially by a number of units, each tuned to a natural frequency of the room Sound amplifier arrangements, each of which has an approximately in the antinode of one of the relevant natural frequency corresponding standing wave attached microphone, one on the relevant Natural frequency tunable filter, an amplifier with a variable below the self-excitation limit of the sound amplifier arrangement Gain factor and one also in the antinode of the relevant standing Includes speaker arranged wave.

Such an arrangement makes it possible to use a correspondingly high number of sound amplifier arrangements an adaptation of the actual value of the reverberation time as a function of the frequency in a very good approximation to one or more predetermined ones To achieve setpoint functions, with a changeover from one to another setpoint function can be reproducible.

The invention is explained in more detail below with reference to the drawings. It shows

F i g. 1 the relative amplitude of sound waves (in dB) as a function of the frequency in the range from 400 to 500 Hz at a specific point in the space reserved for the audience in the Royal Festival Hall in London,

80S 570/382

2 shows an exemplary embodiment of an auditorium equipped with an arrangement according to the invention in longitudinal section and in schematic representation,

3 shows the reverberation time as a function of the relative gain (in dB) of _{a pure sine tone of 100 Hz 3} generated with a loudspeaker on the podium of the Royal Festival Hall in London

4 shows the reverberation time as a function of frequency in the Royal Festival Hall in London with an occupation with listeners of 80% after averaging the measurements at three different locations, where the function specific to the hall and the function achieved with an arrangement according to the invention are shown in dashed lines are shown in solid lines,

FIG. 5 is a diagram similar to FIG. 4, but at empty hall.

From Fig. 1 shows that the relative amplitude of sound waves in the considered lecture hall (Royal Festival Hall in London) because of the strong natural frequencies changes as the frequency F tion unk is subjected to what effect on the reverberation time as a function of frequency.

The lecture hall shown in Fig. 2 comprises a podium 1, an end wall 2, a conventional sound reflector 3 above the podium 1, a floor 4, which is seated in areas 5, 6, one seated Gallery 7, a back wall 8 and a room ceiling.

Two standing sine waves 10, 11 each corresponding to a natural frequency of the hall are shown. wherein the shaft 10 is approximately vertical to the walls 2.8 and the shaft 11 vertical to the Floor 4 run.

The shaft 10 is assigned a sound amplifier arrangement 12 matched to its frequency, which is a mounted in an antinode of the shaft 10 microphone 13, a frequency of the Shaft 10 tunable filter 16, an amplifier

14 with a variable lying below the self-excitation limit of the sound amplifier arrangement 12 Gain factor and one also in the antinode of the relevant standing Shaft arranged speaker 15 includes. The gain of amplifier 14 is medium an adjustable phase shifter 17 can be changed.

An arrangement 12 ″ assigned to the shaft 11 corresponds with respect to its components 13 α, 14 α,

15 ß, 16 α, 17 α of the arrangement 12 and is on the Frequency of wave 11 matched.

The tunable filter 16 or 16 a can optionally consist of an electrical filter, for example an electrical network, an electromechanical filter, for example a tuning fork or tuned tongue, or the microphone 13 or 13 α surrounding Helmholtz resonator. The arrangement with a Helmholtz resonator results in a particular advantage in terms of shielding Interference frequencies.

To achieve the best possible adaptation of the actual value function of the reverberation time to a given setpoint function to achieve, the tuning frequencies of the sound amplifier assemblies 12 are set so that that they are only a few Hertz apart in a covered frequency range. Around on the other hand, to achieve a reasonable expense and the number of sound amplifier arrangements 12 To keep as low as possible, only those frequency ranges are covered, which are for the entire Sound image are essential. Since at low frequencies the reverberation time is essentially independent of the spatial shape of the lecture hall is determined almost exclusively by the absorption of the air According to a preferred embodiment of the invention, the tuning frequencies of the sound amplifier arrangements 12 in a frequency range> 2 kHz, preferably> 1 kHz.

The loudspeaker 15 of a sound amplifier arrangement does not necessarily need to be exactly one To be arranged antinode of the associated standing wave, but the attachment of the Loudspeaker can after other considerations of expediency (for example attachment to a chandelier in the room). A compensation of the local situation compared to the Anti-vibration can be achieved within limits by setting the phase shifter 17.

Furthermore, the expenditure for the arrangement according to the invention can thereby be further reduced reduce the fact that several sound amplifier arrangements 12 tuned to different frequencies at least have a common loudspeaker 15. The loudspeaker is transmitting in this case a frequency mixture of the waves picked up by different microphones 13.

In order to reduce the effort for the amplifiers 14 contained in the sound amplifier arrangements 12 to be reduced are the loudspeaker or loudspeakers assigned to these sound amplifier arrangements 15 to one or more discrete frequencies (if a loudspeaker has several sound amplifier arrangements or microphones 13 is assigned).

From Fig. 4 and 5 it follows that in one and the same Setting of an arrangement according to the invention installed in the Royal Festival Hall in London A considerable increase in reverberation time can be achieved both in a hall that is 80% occupied and in an empty hall can.

Claims (7)

Patent claims: 1. Arrangement for the controllable increase of the reverberation time of a lecture hall without structural Change of space, characterized by a number of each with a natural frequency of the room tuned sound amplifier arrangements (12), each of which is approximately in the antinode of a standing corresponding to the natural frequency in question Microphone (13) attached to the shaft, a filter that can be tuned to the relevant natural frequency (16), an amplifier (14) with one below the self-excitation limit of the sound amplifier arrangement (12) lying changeable gain factor and one also in the antinode of the respective standing Shaft arranged loudspeaker (15) comprises. 2. Arrangement according to claim 1, characterized in that the tuning frequencies of the Sound amplifier arrangements (12) in a frequency range <C 1 kHz, preferably < 1 kHz. 3. Arrangement according to claim 1 or 2, characterized in that the tuning frequencies of the sound amplifier arrangements (12) in the covered frequency range only by a few Hz apart. 4. Arrangement according to one of claims 1 to 3, characterized in that the tunable Filter (16) optionally from an electrical filter (electrical network), an electromechanical one Filter (e.g. tuning fork, tuned tongue) or a Helmholtz resonator surrounding the microphone (13). 5. Arrangement according to one of claims 1 to 4, characterized in that the gain factor of the amplifier (14) can be changed by means of a phase shifter (17). 6. Arrangement according to one of claims 1 to 5, characterized in that several on Sound amplifier arrangements (12) tuned to different frequencies at least one common Have speakers (15). 7. Arrangement according to claim 6, characterized in that one or more sound amplifier arrangements (12) or microphones (13) associated speakers (15) is tuned to one or more discrete frequencies. Considered publications:
"Philips' Technische Rundschau" magazine, 21st year, 1959/60, No. 3, p. 78 and 79 and especially p. 80 and 81. 1 sheet of drawings 809 570/382 7.68 © Bundesdruckerei Berlin