FI75942C - Device for attenuation of sound and acoustic noise - Google Patents

Description

75942

SOUND AND ACOUSTIC NOISE REDUCTION DEVICE - ANORDINATION FOR SOUND AND ACOUSTIC NOISE

The invention relates to a device for attenuating sound and acoustic noise, which device comprises a configuration of acoustic absorbers which prevent unwanted sound from passing through the configuration.

Acoustic noise and high noise levels are a major environmental problem that is of growing interest. Various measures have been taken to reduce the problem. One common measure has been to use barriers with different configurations to prevent sound propagation. Such barriers include, for example, reflective and / or damping sound barriers, 2- and 3-layer insulating glass in windows, sound-absorbing coatings and intermediate insulation in buildings, machinery and vehicles.

The above measures have various disadvantages: they cause permanent installation and / or structural change, they also affect the transport of people, animals, organisms, heat, electricity and air across the sound-absorbing border.

they are ill-suited for temporary installation / removal.

It is also known to use so-called anti-sound systems to prevent sound propagation. Echo systems are characterized in that electrical energy is supplied to the electroacoustic transducers so that a sound field is generated which interferes with the incoming sound field and attenuates or correspondingly amplifies this field at different locations.

In addition, various acoustic absorbers are known for attenuating or eliminating sound. Such absorbers or sound canceling arrangements are known, for example, from U.S. Patents 2,502,017 and 2,502,019. These known devices are especially intended for indoor use, sound absorption in living rooms or other spaces. The individual absorbers according to these patents are hollow bodies, the natural frequencies of which are determined by the mechanical dimensions of the absorbers.

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In optics, the propagation of electromagnetic waves, the propagation of waves in elastic material and gravitational waves, it is further known that it is possible to detect or form so-called point absorbers (light resonance absorption atoms, antennas, vibration dampers or is greater than the point absorber 's own geometric dimension. This is only true when the frequency of the incoming wave causes the absorber to operate in the resonant mode.

The above principle applies in particular to conventional antennas for electromagnetic waves, and in addition to recent developments in a wave power plant. In acoustics, these principles have, to the best of the applicant's knowledge, been used only in so-called acoustic filters.

The object of the invention is to provide a device which makes it possible to prevent the propagation of sound and noise without the above-mentioned disadvantages of the prior art associated with the elimination of sound.

To accomplish this, there is provided a device as defined in the preamble comprising a configuration of acoustic absorbers which prevent unwanted sound from passing through the configuration. It is characterized in that the absorbers consist of electroacoustic transducer-type transducers whose transfer functions are calculated on the basis of measurements of the attenuated sound field and by means of advanced computer programs for calculating said transfer functions.

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By the term "electroacoustic, point absorber type transducer" is meant that the characteristic dimensions of the transducers are significantly smaller than the wavelength, i.e., they are not diffraction type absorbers.

The term "transfer functions" refers to the relationship between the incoming audio signal and the electrical signal supplied by the converter to the electrical energy consuming element.

Electroacoustic transducers can be of any known type, but are, for example, electrodynamic, electromagnetic, capacitive, piezoelectric or piezoresistive.

With regard to the above-mentioned anti-sound system, it should be noted that the device according to the invention is substantially different from the anti-sound system, because in principle no energy is supplied or added to the sound field in the device according to the invention.

The invention utilizes electroacoustic, point-absorber-type transducers arranged in one-, two-, or three-dimensional local configurations or systems. Electroacoustic transducers can be microphones of small and inexpensive construction. The most important types of microphones are electrodynamic microphones, capacitive microphones, carbon dust microphones, piezoelectric or piezoresistive microphones, etc. The microphones are tuned to one or more desired resonant frequencies and transmission functions. The tuning of an individual microphone is done by means of its mechanical dimensioning and / or by an electrical device connected to the microphone output. The electrical devices can be, for example, known passive or electric filters.

Configurations for multiple microphones can also be assigned natural frequencies in addition to the natural frequencies of individual microphones. These natural frequencies are selected according to the placement pattern of the microphones in the configuration. Such configurations prevent the propagation of sound and noise without the significant disadvantages previously described in the prior art. In addition, they have the advantage that, by means of electronic methods, they can be given a characteristic or transfer function, which can vary if desired.

The device according to the invention can consist of an almost unlimited number of different configurations. In various configurations, the point absorbers that form part of them may be arranged in a formula or shape suitable for each purpose and which may be calculated by advanced, mathematical calculations.

In the following, the invention will be further explained with reference to the accompanying drawings, in which: Figs. 1A and 1B show a longitudinal section and a cross-section of a tube with a row of electroacoustic transducers.

Fig. 2 shows a line corresponding to Fig. 1, in which, however, the others are connected to passive electrical elements.

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Fig. 3 shows a line corresponding to Fig. 1, in which, however, the converters are connected to the active electrical elements.

Fig. 4 shows a tube with two electroacoustic transducers to which a device for calculating and generating a signal for the transducers is connected.

In the drawings, in which the same reference numerals denote the same elements in different figures, a simple but illustrative embodiment of the device according to the invention is used. This is shown in its simplest form in Figures 1A and 1B, which show a part of a tube 1 in which three electroacoustic, point-absorber-type transducers 2 are arranged. The converters consist of microphones and, as shown, have no external connections. The sound or noise will be the direction of arrow A and the microphone transfer functions (resonance-sitaajuudet) is adapted such that the sound in question is effectively reduced as it passes over the microphone. The sound is gradually attenuated as it passes the microphones and is substantially eliminated in the relevant frequency range when using, for example, 5-7 microphones. The disclosed embodiment can be adapted for many purposes, for example to reduce / eliminate vent noise in ventilation ducts.

In the embodiment according to Fig. 2, three microphones 4 are shown, which are arranged in the same way as in Fig. 1, but here each microphone is connected to a passive electric element 5, for example a passive electrostatic precipitator. in a form that affects the transfer functions of the microphones as desired.

Fig. 3 also shows a configuration corresponding to Fig. 1, but here three microphones 6 are connected to the active electrical elements 7 in order to apply a suitable effect to the transfer functions of the microphones.

Figure 4 shows two microphones 8 arranged respectively in the microphones of Figures 1-3. However, in this embodiment, the microphone outputs are connected to the input of a device 9, which device calculates and generates an electrical signal from the input signal, i.e. the energy absorbed by the transducers 8, to the transducers to affect their transmission functions. The device 9 may consist essentially of a microprocessor for calculating said signal, and an amplification circuit for supplying the signal at a suitable level to the converters.

As will be appreciated, the devices of the invention can be adapted for many different purposes. Some additional examples are mentioned below, in which point-absorber-type electro-acoustic transducers, possibly with electrical connections, are referred to as point-absorbers only to shorten them.

1) Attenuation of sound coming through an open window: one or more point absorbers are suspended in a suitable (calculated) configuration in the window opening.

2) Sound attenuation by placing a point absorber in a window frame or frame: this allows sound attenuation in both open and closed windows.

3) Attenuation of noise from machine structures, buildings, etc .: the support structures (fixed or mobile) are equipped with point absorbers at the intersections of the support wires. The support wire should be electrically conductive (steel, aluminum, or synthetic fibers with conductive wires, e.g., stainless steel, iron, copper, carbon, etc.).

7 75942 4) Sound attenuating curtains: Conductive wire nets are designed as curtains equipped with a point-absorber configuration to attenuate sound / noise around living rooms, around permanent or temporary sound sources in living rooms, apartments, outdoors, etc.

5) Noise reduction from road traffic: Partially polluting sound barriers, which are currently located, especially along particularly busy roads, can be replaced by real or light column rows with point absorber configurations. It is possible to make these devices self-detecting, i.e. they are, for example, provided with light signals which constantly indicate the current sound level.

Claims (5)

8 75942 A device for training sound and acoustic noise, comprising a configuration of acoustic absorber relays which prevent the desired sound from passing through the configuration, characterized in that the absorber consists of an electroacoustic , and advanced computer programs for calculating said transfer functions. Device according to Claim 1, characterized in that the transfer function of the at least one transducer (2) is defined only by its electrical and mechanical dimensions. Device according to Claim 1 or 2, characterized in that the at least one transducer (4) is connected to passive electrical elements (5) which affect its transfer function. Device according to Claim 1, 2 or 3, characterized in that the at least one converter (6) is connected to active electrical elements (7) which affect its transfer function. Device according to one of Claims 1 to 4, characterized in that a device (9) is connected to at least one of the converters (8), which calculates and generates an electrical signal from the energy absorbed by the converter, which is fed to the converter (8) and affects its transmission function.