FI94565C - Device to be used for changing the acoustic properties of a room space - Google Patents

Description

1 94565

The present invention relates to a device for use in changing the acoustic properties of a room, comprising a pressure sensor, a loudspeaker and an electronic control circuit adapted to produce an electrical signal based on pressure changes in the room which, when reproduced through the loudspeaker, seeks to cancel the pressure sensor. In the context of this application, a loudspeaker means an assembly of one or more loudspeaker elements, which loudspeaker elements may operate in different frequency ranges.

Often, in the pursuit of good sound reproduction, 15 attention is paid exclusively to the features of the sound reproduction equipment. The listening mode also has a very big impact on what the music sounds like. In most cases, the listening room is the biggest factor influencing sound reproduction.

*. The acoustics of the listening room can be improved, for example, by using various acoustic panels for wall and ceiling upholstery. Such passive methods are difficult to implement at frequencies below 200 Hz. As a solution to the problems caused by low frequencies, the apparatus described in the introduction has been proposed, with the aid of which it is possible to attenuate or eliminate room resonances. This is based on the device's ability to cancel low frequency sound waves. When placed in a corner of the room, the device is able to attenuate standing waves in the corner. Early reflections at higher frequencies and .. JO echo significantly affect the nature of the space as a "listening space. A device such as that described in the introduction has no effect on the characteristics of the space in this respect. Typically, normal room space has too few early reflections and too little reverberation.

The device according to the invention also affects the characteristics of the room space at frequencies above 200 Hz. The device according to the invention also includes a space generator adapted to receive an electrical signal proportional to the sound present in the room and to generate a signal based on said signal which, when reproduced through a loudspeaker, generates a sound field in the room with reflections and reverberation. The state generator receives an electrical signal proportional to the sound in the room, either directly from the audio equipment or by means of a microphone included in the device, which is most preferably the same component that acts as a pressure sensor in connection with the control circuit. The pressure sensor is thus most preferably a pressure sensor microphone.

The device according to the invention will now be described in more detail with reference to the accompanying drawing, in which Figure 1 shows a device according to the prior art, in particular for low frequency room resonance attenuation, Figure 2 shows a device according to the invention for changing room acoustic properties, Figure 3 shows a room with the signal generated by the state generator of the device according to

Figure 1 shows a prior art · * 25 circuit for actively attenuating low frequency room resonances. This circuit comprises a pressure sensor microphone 1 adapted to supply a control circuit 3, the output of which is connected to a loudspeaker 2. The pressure sensor microphone 1 detects the pressure prevailing in the room at the location of the device. The control circuit 3 tries to hold the pressure sensor microphone 1 »-:. the pressure experienced at zero by generating a signal which, when reproduced through the loudspeaker 2, cancels the pressure at the pressure sensor microphone 1. This creates a so-called acoustic throat. If the pressure sensor microphone 1 has a positive pressure peak (sound wave), the cone of the speaker 2 moves backwards, so that the pressure at the microphone 1 decreases. The device thus "sucks" the sound wave into itself. Placed in a corner of a room, the effect is the loss or attenuation of room resonances. In practice, several such devices are needed in the room and the operating frequency range is about 20 to 200 Hz.

Figure 2 shows a device according to the invention for changing the acoustic properties of a room. This device according to Figure 2 comprises, as a basic starting point, the device according to Figure 1 as a whole. In addition, a state generator 4 is included in the device 10, which also supplies its output to the speaker 2. Thus, the outputs of the control circuit 3 and the state generator 4 are summed at point 6. It should be noted that in the known solution according to Figure 1 the speaker 2 can only be a low frequency 15 speaker. However, in the device according to the invention, the loudspeaker 2 must be able to reproduce the entire frequency range of the hearing range, i.e. about 20 to 20,000 Hz. In the device according to the invention, the state generator 4 is adapted to receive its control signal, which should be a signal proportional to the sound occurring in the location of the device, either directly from the sound reproduction equipment 5 or from the pressure sensor microphone 1.

Figure 3 shows the sound waves occurring in the room when the listener 7 and the sound source 8 are placed 25 centrally in the room opposite each other. In this case, the listener 7 first receives from the sound source 8 a direct sound wave marked with a large arrow and, in addition, temporal reflections marked with solid lines and reverberations marked with dashed lines. There should be enough early reflections as well as reverberations. · The backing must be sufficiently tight and durable long enough. In this case, the music played in a room equipped with the devices according to the invention may sound the same as, for example, in a concert hall. Since there are too few early reflections and too few and short reverberations in the conventional room 35, the state generator 5 4 94565 is adapted to generate signals such as those described in Fig. 4. In the figure, on the time axis t to the left, a direct sound is depicted, which the state generator receives either directly in electronic form from the sound reproduction equipment 5 or by "listening" to the room space by means of a microphone such as a pressure sensor microphone 1. Based on the received signal, the state generator 4 generates the signals, which in Fig. 4 are designated as early reflections and reverberations. These are signals corresponding to direct sound 10, which, however, are suitably delayed and attenuated.

The echo generated by the state generator should be adapted to the room's own echo so that the end result is optimal. For this reason, the state generator is most preferably able to generate several different types of signal patterns corresponding to Fig. 4, in which the numbers and power levels of early reflections vary to some extent, as do the levels and numbers of reverberation signals. By adjusting the level and number of early reflections, as well as the level and number of reverberant signals, you can have a significant effect on what the music sounds like in that room.

The device according to the invention has been described above mainly schematically by means of one exemplary embodiment. * It is to be understood that the device described can be implemented by a wide variety of electronic solutions without departing from the basic idea of the invention as defined in the appended claims.

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Claims (6)

Apparatus for use in changing the acoustic properties of a room space, which apparatus comprises a pressure transducer (1), a speaker (2) and an electronic control circuit (3) arranged to produce a basis of pressure changes occurring in the rune. electrical signal, which is transmitted via the speaker, strives to eliminate the pressure change detected by the pressure transducer (1), characterized in that the device further comprises a room generator (4) arranged to receive an electrical signal proportional to the noise and pk basis thereof. signal generating a signal, which is transmitted via the loudspeaker (2) to produce an early reflection and after sound containing sound field in the room. 2. Device according to claim 1, characterized in that the room generator (4) receives an electrical signal proportional to the sound from a sound reproducing apparatus (5). Device according to claim 1, characterized in that the room generator (4) receives an electrical signal proportional to the sound present in the room from said pressure transducer (1). Device according to any of claims 1-3, characterized in that the pressure transducer is a pressure microphone (1). Device according to any of claims 1-4, characterized in that the loudspeaker is a loudspeaker (2) for the entire sound range. • ·