JPS5938797B2 - television audio receiving device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a sound field expansion device for a television audio multiplexed signal reception device using a delay element driven by a clock pulse, such as a BBD element.
This relates to setting the frequency of the driving clock pulse.

FIG. 1 is a block diagram of a sound field expansion circuit in a conventional television audio multiplex receiver.

Here, 1 is an indirect sound synthesis circuit, 2 and 5 are reduction filters, 3 is a BBD element delay element 4 is an oscillation circuit that generates a clock pulse for driving the delay element, 6 is an indirect sound defeat circuit, and 7 is an indirect sound defeat circuit. It is a control circuit. When such a device receives a stereo signal, the indirect sound synthesis circuit 1 synthesizes the left signal L and the right signal R to create an L-R signal, which is delayed by the delay element 3 and then delayed to the left signal. The obtained L-R signal is added to obtain an L+(L-R)' signal.

Here, (LR)' represents a delayed signal. Similarly, for the right signal, (LR)' is subtracted to obtain an R-(LR)' signal. As a result, the left signal composite output becomes Li-L'-W, which means that the delayed right signal with the polarity reversed is added, and the right composite signal output also becomes R+W-L', which is delayed. This means that the left signal with the polarity reversed is added. In this way, the acoustic crosstalk components generated when the left speaker signal reaches the right ear with a slight delay from the left and right speaker outputs, and the acoustic crosstalk components that occur when the right speaker signal reaches the left ear with a slight delay, are added to the above composite signal. By canceling out the signal with the other signal, which is delayed and has reversed polarity, the sound field can be expanded. The delay time at this time is determined by the distance between the two speakers, the listening distance, the distance between both ears, and the like. On the other hand, when receiving a monaural signal, the indirect sound synthesis circuit 1 passes only one of the left and right signals.

(In the case of a monaural signal, the L signal and R signal are equal.)
. This signal is delayed and added to the direct sound signal in one system and subtracted from the direct sound signal in the other system. As a result, if the phase matches the delayed indirect sound in the audio signal band, the amplitude of the synthesized signal increases, and at that time, since the phase of the other signal output differs by 1800, the amplitude of the synthesized signal decreases. Therefore, the sound source shifts to the right or to the left depending on the frequency component, and as a result, a sound field expansion effect is added. In the above operation, the band of the indirect sound signal is limited by the clock frequency of the delay element 3.

This is because if the frequency is set to a sufficiently higher frequency than the audio signal band, the band will not be limited, but the number of stages of BBD elements etc. must be increased, making it uneconomical. A method has been adopted in which the number of stages is reduced, the clock frequency is lowered, and the delay time is increased. For example, conventionally, a 128-stage BBD
The tarok frequency is selected to be the television horizontal scanning frequency FH (15,734 KHz) to obtain a delay time of approximately 4 ms. At this time, the clock frequency must be synchronized with FH or stabilized at FH using an extremely accurate oscillation frequency, otherwise horizontal frequency components and beads contained in the audio signal of the television signal would be generated, causing an unpleasant sound. Furthermore, television audio signals also include 2fH components, especially when receiving multiple audio signals.
Since residual H subcarrier components are included, a bead between these and the second harmonic of the clock pulse is also generated. Furthermore, by setting the clock frequency to FH, the band of the indirect sound signal is substantially limited to about 2 KHz.
This is due to the relationship with the practical configuration of the reduction filter.
This is because two or more signal components are sufficiently attenuated to suppress the bead with the clock frequency. It is possible to widen the band a little more and use a low-pass filter that attenuates sharply, but this method has not received good reviews in terms of sound quality during indirect sound synthesis and sound field expansion effect. Therefore,
The present invention aims to eliminate these drawbacks by setting a new clock frequency for the delay element in such a sound field expansion circuit, thereby enhancing the sound field expansion effect. In other words, the clock oscillation frequency of a delay element such as a BBD element is set to (2n+1)/2 times the horizontal frequency FH (n is a natural number).
By setting it to
)/2×FHZ (m-n no 11FH (m is a natural number),
In other words, only bead components that are an integral multiple of 1 are generated.

Here, the oscillation frequency of the clock pulse is set to 3/2X, for example.
If fH-23,601KHz, the bead component is 7.
867 KHz and its high frequency components. As a result, the band of the indirect sound signal can be expanded to approximately 3 KHz, as determined from the sampling relationship with the conventional clock frequency. At the same time, the bead component with the horizontal frequency component can also be attenuated. Furthermore, frequency stability is no longer required to be as accurate as in the past. However, in order to obtain a delay time equivalent to the conventional one, it is necessary to use delay elements with 1.5 times as many stages as the conventional BBD element, etc. The delay time of indirect sound when receiving a stereo broadcast is determined by the distance between the left and right speakers, the listening distance, the distance between both ears, etc. For example, if the speakers are placed on both sides of the TV receiver, the optimal delay time is The delay time is about 60 to 120 μSec, and the delay time when receiving monaural broadcasting is about several Msec. Conventionally, as shown in FIG. 1, switching the delay time between stereo and monaural has been accomplished by using a BBD element and switching its clock frequency using a stereo control signal. Clock oscillation in monaural mode requires high stability as described above, and oscillation in stereo mode does not require as high stability as in monaural mode, but it is necessary to manage or adjust the oscillation frequency. FIG. 2 is a block diagram of the main part showing one embodiment of the present invention.
Portions corresponding to those in the figure are given the same reference numerals.

In this circuit, as the delay element 3, a monaural delay element 3M using a BBD element etc. with a large number of stages and a BBD element with a small number of stages are used.
A stereo delay element 3S using a BD element or the like is provided and connected in parallel, and their respective outputs are added to the switching circuit 8, where the output of either delay element 3M or 3S is controlled by a stereo control signal. I switch between monaural and stereo by switching whether to take it out or not.

Then, the same clock pulse for one drive is applied from the clock oscillation circuit 4 to both delay elements 3M and 3S, and the oscillation frequency of the clock pulse is set to (2n+1)/2 of the horizontal frequency FH as described above. I try to do that. As described above, according to the present invention, there is no bead interference between the horizontal scanning frequency component and its harmonic components in the television audio signal, and it is useful for successfully receiving audio multiplex broadcasting, etc. It is possible to realize a device that is

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a conventional device, and FIG. 2 is a block diagram of a television audio receiving device according to an embodiment of the present invention. 1... Indirect sound synthesis circuit, 2, 5... Low-pass filter, 3... Delay element, 4...
Clock oscillation circuit, 6... Indirect sound default circuit, 7... ．． Indirect sound default control circuit, 8...
...Switching circuit.

Claims (1)

[Claims] 1. Two audio signal systems, left and right, are provided in a circuit for receiving television audio signals, the respective audio signals are synthesized, an indirect sound signal is created by an indirect sound generation circuit including a delay element, and the indirect sound signal is At the same time, the oscillation frequency of the clock for driving the delay element is changed to (2n+) of the horizontal scanning line frequency.
1) A television audio receiving device characterized in that the setting is set to 1)/2 times (where n is a natural number).