JPS6321199B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention eliminates the harmful effects of reflected sound in a room, etc.
An object of the present invention is to provide an acoustic transmission characteristic correction device that can improve sound quality at a listening point.

Figures 1A and B show the speaker listening conditions in a room, where 1 is the room, 2 is the speaker placed in this room 1, 3 is the listener in room 1, and the sound emitted from speaker 2 is shown. Sound reaches the listening point via direct sound path D, and also passes through many reflected sound paths.
The listening point is reached via ID ₁ , ID ₂ , etc. The reflected sound that reaches the listening point via the reflected sound paths ID ₁ , ID _{2 .} . . arrives later than the direct sound that reaches the listening point directly via the direct sound path D. If the delay time of this reflected sound is several tens of milliseconds or more, the reflected sound will be heard separately from the direct sound, but if the delay time of the reflected sound is less than several tens of milliseconds, the reflected sound will affect the direct sound. Deteriorates the sound quality at the listening point. The reflected sound shown in Figures 1A and B is the first reflected sound that has been reflected once from walls, floors, etc., and the path difference between the path of this first reflected sound and the direct sound path is small, and the first reflected sound The time difference and level difference between the sound and the direct sound are small, and the reflected sound interferes with the direct sound, causing peaks and dips in the sound pressure frequency characteristics at the listening point, as shown in Figure 2, and deteriorating the sound quality. Become.

In order to remove the peaks and dips in the sound pressure frequency characteristics at the listening point in the room as described above, there have been attempts to use a graphic equalizer with the characteristics shown in Figure 3, but it is difficult to completely correct it, and If the difference between peak and dip exceeds 20 dB, there are drawbacks such as increased burden on the electrical circuit.

The present invention attempts to eliminate the above-mentioned drawbacks of the prior art by generating sound that cancels reflected sound.

For example, when a signal S as shown in Fig. 4 is applied to a speaker and sound is emitted from the speaker, this sound S _D reaches the listening point after τ ₀ via a direct sound path as shown in Fig. 5. , further after τ ₁ g(0
<g<1) One of the reflected sounds S _ID that has been attenuated reaches the listening point. To cancel this reflected sound S _ID , the sixth
As shown in the figure, after τ ₁ , the negative phase cancellation signal is multiplied by g.
Just apply S′ to the speaker. This canceling signal
S' is converted into sound by the speaker and reaches the listening point as a direct sound S' _D after (τ ₀ + τ ₁ ), and as shown in Figure 7, the reflected sound S _ID of the signal S is the direct sound of this canceled signal.
Cancelled by S′ _D. S′ _ID is the reflected sound of the canceled signal S′, and is attenuated by ^twice g. FIG. 8 shows the situation after S _ID is canceled by S' _D at the listening point.

FIG. 9 shows a circuit for canceling the reflected sound. In Fig. 9, 1 is an input terminal, 2 is a delay circuit that delays the signal applied to input terminal 1 by τ ₁ , 3 is a phase inversion circuit that inverts the phase of the delayed signal by 180°, and 4 is the reflection wall itself. An equalizer that simulates the transfer function of 5, 5 is g(0
<g<1) times, and the output of this gain adjuster 5 is added to the input signal in an adder 6 and applied to a speaker via an output terminal 7.

In this way, the reflected sound S _ID of magnitude g can be canceled, and the influence of the reflected sound on S′ _ID of magnitude g ² can be reduced. Furthermore, in order to cancel the cancellation sound S' _ID , it is necessary to apply a cancellation signal of magnitude g ² to 2·τ ₁ . Completely canceling out the reflected sound by successively generating cancellation signals in this manner can be achieved by using a feedback loop.

FIG. 10 shows an embodiment of the present invention, in which a feedback loop 8 is provided for feeding back the output of the gain adjuster 5 to the input stage of the delay circuit 2, as shown in FIG. Note that 9 is an adder.

When the signal shown in Fig. 11 is applied to the input terminal in Fig. 10, the signal at the output terminal 7 is delayed by τ ₁ and attenuated by g (0<g<1) times, as shown in Fig. 12. Delayed signals are obtained sequentially. These signals are respectively applied to speakers and converted into sounds, which successively reach the listening point as direct sounds after a certain period of time, as shown in FIG. On the other hand, the signal shown in FIG. 12 is emitted from the speaker, and the reflected sound reflected from walls etc. reaches the listening point one after another as shown in FIG. 14. The direct sound shown in FIG. 13 cancels the reflected sound shown in FIG. 14. Therefore, as shown in FIG. 15, only the desired signal can be obtained at the listening point.

Furthermore, the difference between Figures 9 and 10 is that the feedback loop 8
The configuration can be easily changed to the configuration shown in FIG. 9 by cutting the feedback loop 8. In other words, there is a possibility that the feedback loop 8 generally oscillates, and for example, in FIG.
Oscillation may occur during adjustment of the equalizer 4 and gain adjuster 5, or due to changes in the listening position, speaker position, or reflecting wall position, and the speaker may be damaged due to the oscillation. In such a case, there is an advantage that the oscillation can be stopped easily and quickly by cutting the feedback loop 8 shown in FIG. 10, and that the S _ID shown in FIG. 5 can be corrected to some extent. Further, during the above-mentioned adjustment, the feedback loop 8 can be disconnected, and after rough adjustment is performed, the loop can be connected to perform fine adjustment. This advantage is due to the fact that the feedback loop 8 is provided independently of important components such as delay elements that simulate the reflected sound transmission system.

Note that the above embodiment is a circuit for removing reflected sound via one reflected sound path, but in order to remove the influence of reflected sound on other reflected sound paths, the first
The circuit configuration shown in FIG. 6 may be used. Figure 17 shows the equivalent transmission frequency characteristics of the circuit shown in Figure 16. By using the circuit shown in Figure 16, the peaks and dips in the characteristics shown in Figure 2 can be removed, resulting in improved sound quality at the listening point. This is something that can be improved.

The device of the present invention has the above-described configuration, and according to the present invention, it is possible to eliminate the adverse effects of reflected sound at the listening point in the room and improve the sound quality. Furthermore, it is possible to cope with other oscillations while maintaining the correction effect to some extent during adjustment.

[Brief explanation of drawings]

Figures 1A and B are top and front views respectively showing indoor speaker listening conditions, Figure 2 is an indoor transmission frequency characteristic diagram, Figure 3 is a graphic equalizer frequency characteristic diagram, and Figures 4 to 8. The figures are an explanatory diagram of the operation of a conventional acoustic transmission characteristic correction device, and
FIG. 9 is a block diagram of a conventional acoustic transmission characteristic correction device, FIG. 10 is a block diagram of an acoustic transmission characteristic correction device according to an embodiment of the present invention, and FIGS.
16 is a block diagram of another embodiment of the present invention, and FIG. 17 is an equivalent transmission frequency characteristic diagram of the same device. 1...Input terminal, 2...Delay circuit, 3...Phase inversion circuit, 4...Equalizer, 5 Gain adjuster,
6... Adder, 7... Output terminal, 8... Feedback loop, 9... Adder.

Claims (1)

[Claims] 1. A forward signal consisting of a delay circuit that delays an input signal, a phase inversion circuit that inverts the phase of the delayed signal, an equalizer that arbitrarily sets the gain frequency characteristics of the phase-inverted signal, and a gain adjuster. a transmission circuit; a reverse signal transmission circuit comprising a feedback loop that feeds back the output of the gain adjuster to the input of the delay circuit; and an adder that adds the output of the gain adjuster and the input signal. . An acoustic transmission characteristic correction device, characterized in that the reverse direction signal transmission circuit can be arbitrarily disconnected.