To avoid degradation of the acoustic signal radiated from the opening of the ducted horn of a ducted horn type speaker, under influence of the ducted horn, below the characteristic of the speaker itself, and input terminal for receiving an audio signal, a non-recursive digital filter for varying the input audio signal, a power amplifier for amplifying the varied signal, and speaker for replaying the amplified signal are provided. The non-recursive digital filter realizes the inverse characteristic of the transfer characteristic of the ducted horn.
An automatic sound field correcting device applies signal processing onto audio signals of plural channels and outputs processed audio signals to corresponding plural speakers. The automatic sound field correcting device includes: a noise measuring unit for measuring environmental noise level; a signal level determining unit for determining a measurement signal level based on the environmental noise level; and a correcting unit for outputting a measurement signal having the determined measurement signal level to perform automatic sound field correction.
An acoustic pulse in size corresponding to the digit position of a digital signal pulse is generated by means of condenser speakers 26.sub.1, 26.sub.2, . . . 26.sub.n, that are grouped electro acoustic transducer elements corresponding to each bit that forms a digital signal employed in a communication channel. Then, an electro acoustic D/A converter for synthesizing the pulse in a cavity 24 is composed. Further, this electro acoustic D/A converter is to be as a component, and an electro acoustic A/D converter is composed by additionally providing electric accessories as in the A/D converter comprising a general electric circuit. In this manner, a transmitter/receiver having a function for converting between an acoustic analog signal and a digital electric signal is composed.
A sound compensation system alters an electrical audio signal for input to a sonic reproduction device having associated behavioral characteristics. The behavior characteristics of the device are defined by individual or groups of individual components of the sonic reproduction device and include mechanical, acoustic and electromagnetic behaviors. The model includes a plurality of filters that simulate at least one of the behavior characteristics of the sonic reproduction device. The filters are defined by digital signal processes or by analog circuits and are characterized by one or more of an associated frequency, time, phase and transient response. These responses combine to define an overall response for the model. The filters include adjustable parameters which are used to alter filter responses to produce responses that are conjugates to the responses of the unaltered filters and thus the sonic reproduction device. A controller modifies the parameters.
A loudspeaker unit which requires no particular procedure for correction of the acoustic characteristic even if the installation environment of the loudspeaker unit changes, and which can correct, in addition to the frequency characteristic, a sound lag and a phase shift ascribable to the reverberation and an echo of a sound. The loudspeaker unit picks up a sound regenerating from the loud speaker with a microphone, and compares in real time a sound from a sound source with a regenerative sound, referring to a difference therebetween, with reference to the characteristic at an optional frequency and the characteristic of the reverberation or the echo each including the delay time, respectively, and corrects the signal to be sent to the loudspeaker by the result of arithmetic.
The present invention relates to the implementation of a digital adaptive equalizer for a T1/E1 long haul transceiver which is capable of adapting to a wide range of cable types, cable lengths, and/or other data transmission impairments, particularly when the transmission path type and/or length are unknown. The digital adaptive equalizer contains two filter blocks, i.e., an IIR filter and a FIR filter, together with a filter selector block to select a best IIR filter based on an error estimation of the received data. Only a few sets of coefficients are found to be necessary to allow proper digital equalization of a large number of cable types and/or lengths. A filter selector block selects a desired set of coefficients corresponding to the optimum IIR filter. The coefficients may be programmed into volatile memory (e.g., RAM) or non-volatile memory (e.g., Flash). Alternatively, the coefficients may be hardwired into the IIR filter. The back end of the digital adaptive equalizer contains an adaptive finite impulse response (FIR) filter. In the disclosed embodiment, the FIR filter uses a least mean square (LMS) algorithm for adaptation to the unknown or changed T1 or E1 transmission channel or medium. The adaptive FIR filter adjusts the output from the IIR filter to accurately match the inverse response of the unknown channel used to transmit the received T1/E1 signal. Equalization may be temporarily frozen if periodic patterns are detected in the received T1/E1 signal. A restored T1 or E1 signal is output from the FIR filter, and thus from the digital adaptive equalizer.
