Loudness device

Abstract: A loudness device includes a low-pass filter (LPF) which has a variable cut-off frequency and passes a low frequency band of an input signal; a high-pass filter (HPF) which has a variable cut-off frequency and passes a high frequency band of the input signal; a first synthesizer for synthesizing output signals from the LPF and HPF at a variable synthesizing rate to provide a first synthesized output; and a second synthesizer for synthesizing the input signal and an output from the first synthesizer at a variable synthesizing rate to provide a second synthesized output. In this configuration, the low-pass frequency band can be varied by varying the capacitance of the capacitor of the LPF, the high-pass frequency band can be varied by the resistance of the resistor of the HPF, the attenuation degree in the high-pass frequency band can be varied by varying the resistance of the resistor of the first synthesizer, and the attenuation degree of the intermediate frequency band can be varied.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loudness device used in an audio signal processing system. 2. Description of the Related Art As shown in Fig. 4, a conventional loudness device is composed of a series connection of capacitors 50 and 51 and a variable resistor 52 which are connected in parallel for an input. The connecting point between the capacitors 50 and 51 and the middle point in resistance of the variable resistor 52 are connected to each other. An output is obtained from a sliding piece of the variable resistor 52. Fig. 5 is a graph showing the characteristic when the sliding piece of the variable resistor 52 in the loudness device as shown in Fig. 4 is shifted. In Fig. 5, line A indicates the characteristic when the sliding piece has been shifted to the maximum toward the input terminal. In this case, an input signal is outputted as it is. When the sliding piece is shifted toward the side of grounding, as indicated by line B in Fig. 5, both low frequency and high frequency ranges attenuate. In addition, the intermediate frequency range attenuates more greatly. When the sliding piece is further shifted toward the grounding side, as indicated by lines C and D, the intermediate frequency range attenuates further more greatly than both low frequency and high frequency ranges. In the conventional loudness device, as shown in Fig. 4, the characteristic in each of both low frequency and high frequency ranges is uniquely defined according to setting the attenuation degree in the intermediate range. Therefore, a user cannot control the loudness to the most preferable characteristic. Document Patent Abstracts of Japan JP 02 222207 describes a hearing sense compensation device having fixed cut-off frequencies. It comprises a low pass filter and a high pass filter in order to derive a low frequency band and a high frequency band of the input signal, a first synthesizer having a fixed synthesizing rate to mix the output signals from the low and high pass filter, and a second synthesizer for synthesizing the input signal and the output of the first synthesizer at a variable synthesizing rate. SUMMARY OF THE INVENTION An object of the present invention is to provide a loudness device which can vary the attenuation degree of an intermediate frequency band, cutoff frequency of a low frequency pass-band, cutoff frequency of a high frequency pass-band, and attenuation degree of the high frequency pass-band. In order to attain the above object of the present invention, in accordance with the present invention, there is provided a loudness device comprising: a low-pass filter (LPF) which has a variable cut-off frequency and passes a low frequency band of an input signal; a high-pass filter (HPF) which has a variable cut-off frequency and passes a high frequency band of the input signal; a first synthesizer for synthesizing output signals from the LPF and HPF at a variable synthesizing rate to provide a first synthesized output; and a second synthesizer for synthesizing the input signal and an output from the first synthesizer at a variable synthesizing rate to provide a second synthesized output. In this configuration, the loudness device can vary the attenuation degree of an intermediate frequency band, cutoff frequency of a low-pass frequency band, cutoff frequency of a high-pass frequency band, and attenuation degree of the high -pass frequency band. Preferably, the second synthesizer is a sliding resistor having end terminals to which the input signal and the output signal from the first synthesizer are supplied, respectively and a sliding terminal from which the synthesized output is produced. In this configuration, the attenuation degree of the intermediate frequency band can be easily varied by shifting the position of the sliding terminal. Preferably, the first synthesizer includes an operational amplifier, a first fixed resistor through which the output signal from the LPF is connected, a variable resistor through which the output signal from the HPF is connected, and a second fixed resistor having a resistance equal to that of the first fixed resistor, through which an output from the operational amplifier is fed back to an input thereof. In this configuration, the attenuation degree of the high-pass frequency band can be easily varied by varying the resistance of the variable resistor. The above and other objects and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic circuit diagram of an embodiment of a loudness device according to the present invention; Fig. 2 is a concrete circuit diagram of a filter block in the embodiment of the loudness device; Fig. 3 is a graph for explaining the operation of the loudness device; Fig. 4 is a schematic circuit diagram of a conventional loudness device; and Fig. 5 is a graph showing the characteristic of the conventional loudness device. DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring to Figs. 1 and 2, an explanation will be given of an embodiment of the loudness device according to the present invention. Fig. 1 is a schematic circuit diagram of an embodiment of a loudness device according to the present invention. Fig. 2 is a concrete circuit diagram of a filter block in the embodiment of the loudness device. In Fig. 1, reference numeral 1 denotes a buffer amplifier; 2 a filter block; 3 a second synthesizer for synthesizing an input signal and a filter block output; and 4 a buffer amplifier. The second synthesizer 3 includes a sliding resistor, to both ends of which an input signal (Vi) and an output signal (F(s)Vi) from the filter block 2 are supplied. An output signal is produced from a sliding terminal of the sliding resistor, and supplied to the buffer amplifier 4. The filter block 2, as shown in Fig. 2, a low-pass filter (LPF) 10, a high-pass filter (HPF) 20 and a first synthesizer 30. In the low-pass filter (LPF) 10, the input signal is supplied to an operational amplifier 11 through a resistor R1, and an output from the operational amplifier 11 is fed back to the input thereof through a parallel circuit composed of a resistor R1 and capacitor C1. Therefore, the low-pass filter (LPF) 10 serves as a first order low-pass filter having a time constant of the values of the resistor R1 and capacitor C1. The cut-off frequency of the low-pass filter 10 can be varied by the capacitance of the capacitor C1. In the high-pass filter (LPF) 20, the input signal is supplied to an operational amplifier 21 through a capacitor C2, and an output from the operational amplifier 21 is fed back to the input thereof through a parallel circuit composed of a resistor R2 and capacitor C2. Therefore, the high-pass filter (LPF) 20 serves as a first order high-pass filter having a time constant of the values of the resistor R2 and capacitor C2. The cut-off frequency of the high-pass filter 20 can be varied by varying the resistance of the resistor R2. In the first synthesizer 30, the output from the low-pass filter 10 is supplied to an operational amplifier 31 through a resistor R3, the output from the high-pass filter 20 is also supplied to the operational amplifier 31 through a resistor R4, and the output from the operational amplifier 31 is fed back to the input thereof though a resistor R5 having a resistance equal to that of the resistor R3. Thus, the low-pass frequency band can be varied by varying the capacitance of the capacitor C1 of the LPF 10 ("A" in Fig. 3), the high-pass frequency band can be varied by the resistance of the resistor R2 of the HPF 20 ("B" in Fig. 3), the attenuation degree in the high-pass frequency band can be varied by varying the resistance of the resistor R4 ("C" in Fig. 3) of the first synthesizer 30, and the attenuation degree of the intermediate frequency band can be varied by shifting the sliding position (γ/R) of the sliding terminal of the second synthesizer 3 ("D" in Fig. 3).

Claims: A loudness device with adjustable frequency characteristic including: a low pass filter (10) which passes a low frequency band of an input signal, a high pass filter (20) which passes a high frequency band of the input signal, a first synthesizer (30) for synthesizing the output signals from the low pass filter (10) and the high pass filter (20), and a second synthesizer (3) for synthesizing the input signal and the output signal from the first synthesizer (30) to provide a synthesized output, said second synthesizer (3) being adapted to provide for a variable attenuation of the intermediate frequency band; characterized in that the cut-off frequency of the low pass filter (10) and the cut-off frequency of the high pass filter (20) are adjustable, and the first synthesizer (30) is adapted to provide for a variable attenuation of the high-pass frequency band. The loudness device according to claim 1, wherein said second synthesizer (3) is a sliding resistor having a sliding terminal from which said, synthesized output is collected, and the sliding resistor being supplied at one end with said input signal and at the other end with said output signal from the first synthesizer (30). The loudness device according to claim 1 or 2, wherein said first synthesizer (30) includes: an operational amplifier (31), a first fixed resistor through which said output signal from said low-pass filter (10) is connected, a variable resistor through which said output signal from said high-pass filter (20) is connected, and a second fixed resistor having a resistance equal to that of said first fixed resistor, through which an output from said operational amplifier (31) is fed back to an input thereof.

Inventors: INOHANA HARUYUKI, KAGEYAMA TORU, SASAKI MASARU, SAWAKI MANABU, TAKAMI YUSUKE, INOHANA, HARUYUKI, KAGEYAMA, TORU, SASAKI, MASARU, SAWAKI, MANABU, TAKAMI,YUSUKE, Inohana, Haruyuki, c/o Pioneer Corporation, Kageyama, Toru, c/o Pioneer Corporation, Sasaki, Masaru, c/o Pioneer Corporation, Sawaki, Manabu, c/o Pioneer Corporation, Takami,Yusuke, c/o Pioneer Corporation
Applicants: PIONEER CORP, PIONEER CORPORATION
Application year: 1999
Main classification: H03G5
IPC codes: H04R3, H03G5