Abstract: A stereo receiver of a simple structure is disclosed capable of continuously controlling the degree of separation of left and right voice signals in accordance with the level of electric field strength. The stereo receiver comprises electric field strength detecting means 9 for detecting the electric field strength of a received signal, and a stereo demodulation circuit 5 for outputting original voice signals of left and right channels. A blend circuit 6 is provided for blending the original voice signals with each other to output blended voice signals of the left and right channels. The degree of blending between the original voice signals is continuously changed correspondingly to the electric field strength. As a result, the S/N, which may deteriorate when the electric field strength is low, can be improved with a simple structure.

Abstract: A Japanese BTSC audio broadcast signal has three modes of transmission: mono, stereo, or dual mono. The control channel centering at 3.5 fH is one of the three channels in the J-BTSC signal, and contains information to indicate to the decoder which one of the three modes the audio transmission is in. The present invention uses a bandpass filter directly in the AM band, followed by envelope filtering and a decision circuit. Therefore, the need for AM demodulation and AM carrier detection is eliminated.

Abstract: Provided are a method and apparatus for encoding and decoding a stereo signal or a multi-channel signal. According to the method and apparatus, a stereo signal or a multi-channel signal can be encoded and/or decoded by generating parameters based on a mono signal.

Abstract: Systems provide an audio/visual output to each of a plurality of listeners in a manner that permits individualized audio adjustment, wherein audio comprises a first signal that is substantially voice and a second signal that is substantially other than voice. The systems may include a video device, a storage medium, and a transmitter that transmits the first and second signals to a plurality of personal listening devices. Each of the plurality of personal listening devices may include first and second receivers, first and second adjustment devices, an audio signal combining device, and one or more transducers, wherein the systems permit each of the plurality of listeners to adjust the first and second signals independently of other ones of the plurality of listeners in an audience.

Abstract: The invention enables the inclusion of voice and remaining audio information at different parts of the audio production process. In particular, the invention embodies special techniques for VRA-capable digital mastering, accommodation of PCPV/PCA and/or SCRA signals in audio CODECs, VRA-capable encoders and decoders, and VRA in DVD and other digital audio file formats. The invention facilitates an end-listener's voice-to-remaining audio (VRA) adjustment upon the playback of digital audio media formats by focusing on new configurations of multiple parts of the entire digital audio system, thereby enabling a new technique intended to benefit audio end-users (end-listeners) who wish to control the ratio of the primary vocal/dialog content of an audio program relative to the remaining portion of the audio content in that program.

Abstract: In a device for processing a stereo audio signal having a first channel and a second channel the stereo signal is at first analyzed to obtain a measure for a quantity of bits required by a coder to code the stereo audio signal using a coding algorithm. The first channel and the second channel are then modified when the measure for the quantity of bits is larger than a predetermined value, the modification being performed in such a way that the energy of a sum signal of the first and the second modified channel is in a predetermined relation to the energy of a sum signal of the first and the second channel and that a difference signal of the first and the second modified channel is attenuated in contrast to the difference signal of the first and the second channel.

Abstract: A method for realizing virtual multi-channel by spectrum analysis is disclosed. The low-frequency-effect sound data is obtained by averaging sound data of left and right channels in the two-channel sound source and filtering the average by a first low pass filter. The central channel sound data is obtained by averaging sound data of the left and the right channels in the two-channel sound source and filtering the average by a second low pass filter. The surround right and left sound data is obtained by copying sound data of the left and the right channels in the two-channel sound source, respectively.

Abstract: A method to denoise a stereo signal comprising a stereo sum signal and a stereo difference signal, performs a frequency selective stereo to mono blending based on the masking effect of the human auditory system. Therefore, a stereo signal noise reducer, comprising a first filter bank (1) to split the stereo difference signal (1?r) into a plurality of subbands, respective first multipliers (20, . . . , 2N) to weight each of the subbands of the stereo difference signal with a respective corresponding control signal (C0, . . . , CN), and a first adder (3) to sum all weighted subbands of the stereo difference signal (1?r) to build a frequency selective weighted stereo difference signal (diff), within which a number and width of the subbands obtained via the first filter bank (1) are choosen according to the properties of the human auditory system, further comprises a weighting factor determination unit which determines a respective control signal (C0, . . .

Abstract: The sound reproduction of a multichannel sound reproduction system with a plurality of speakers which is connected to the output of an FM stereo receiver is controlled by a control signal derived from the reception quality. Preferably, the control signal from the FM stereo receiver for controlling the stereo and mono components is also employed to control the multichannel sound reproduction system. For example, stereo, pseudo-stereo or mono reproduction are provided in the multichannel sound reproduction system in response to the stereo component within the output signal.

Abstract: The invention relates to a method of generating a left modified and a right modified audio signal for a stereo system from multichannel audio signals (XL, XR, XLS, XRS, and XC) with a left and a right channel and at least one further audio channel. According to the invention, the signal of the channel of highest energy is modified in a filter (1) with a transformation function in a first parallel branch (2) and is modified in a second filter (6) with a reverberation function in a second parallel branch (5), whereupon the modified signals are joined together in a summation unit (8).

Abstract: A method for providing multiple users with voice-to-remaining audio (VRA) adjustment capability includes receiving at a first decoder a voice signal and a remaining audio signal and simultaneously receiving at a second decoder, the voice signal and the remaining audio signal, wherein the voice signal and the remaining audio signal are received separately; and separately adjusting by each of the decoders, the separately received voice and remaining audio signals.

Abstract: A demodulator (10) converts television signals to video baseband signals and audio baseband signals including stereo signals representing a right channel signal value and a left channel signal value. A DSP (60) recursively finds a preferred coefficient value for a scaling that reduces stereo separation due to amplitude variation of the right and left channel signal values. The preferred coefficient value is thereafter used for scaling the right and left channel signal values.

Abstract: The invention enables the inclusion of voice and remaining audio information at different parts of the audio production process. In particular, the invention embodies special techniques for VRA-capable digital mastering and accommodation of VRA by those classes of audio compression formats that sustain less losses of audio data as compared to any codecs that sustain comparable net losses equal or greater than the AC3 compression format. The invention facilitates an end-listener's voice-to-remaining audio (VRA) adjustment upon the playback of digital audio media formats by focusing on new configurations of multiple parts of the entire digital audio system, thereby enabling a new technique intended to benefit audio end-users (end-listeners) who wish to control the ratio of the primary vocal/dialog content of an audio program relative to the remaining portion of the audio content in that program.

Abstract: A stereo radio receiver has a channel separation stage for setting an optimal channel separation of the left audio channel from the right audio channel, even under sufficient receiving field strength following a time of multipath reception for the duration of the operating time of a timing element, to a reduced (i.e., lesser degree of) channel separation.

Abstract: The invention addresses itself to the task of providing a medium-frequency stereo broadcast receiving circuit that does not require any alteration of the radio wave format used in the medium-frequency stereo broadcast system that has become the de facto standard, and that receives transmitted broadcast waves and removes, in the course of the demodulation process, disturbance that has affected the signal during its propagation, thereby improving the audio quality of the demodulated signal and obtaining the full potential of the stereo effect. To achieve this, the received medium-frequency stereo broadcast wave is converted to a single-sideband signal, and the sum signal (L+R) is demodulated from the phase term of this converted single-sideband signal. The difference signal (L−R) is demodulated from the phase term of the received medium-frequency stereo broadcast wave and from the demodulated sum signal output.

Abstract: A stereo broadcasting receiving device comprises pseudo stereo signal generation means for generating a pseudo left stereo signal and a pseudo right stereo signal from an L+R signal, first multiplication means for multiplying the pseudo left stereo signal by a first coefficient, second multiplication means for multiplying the pseudo right stereo signal by the first coefficient, third multiplication means for multiplying the L+R signal by a second coefficient, fourth multiplication means for multiplying an L−R signal by a third coefficient, coefficient determination means for determining the first coefficient, the second coefficient, and the third coefficient on the basis of the result of judgment in receiving state judgment means, means for generating a left stereo output signal on the basis of an output signal of the first multiplication means, an output signal of the third multiplication means, and an output signal of the fourth multiplication means, and means for generating a right stereo o

Abstract: A method for influencing the channel separation of an audio signal to be reproduced, obtained from a received radio signal, in a radio receiver, as well as a radio receiver for carrying out the method includes an auxiliary field strength signal derived from the received field strength of the received radio signal, and an auxiliary interference signal derived from signals indicating reception interference events, being combined with one another and with an auxiliary channel separation signal that is derived from a signal indicating the frequency of interference events, to yield a factor D which influences the stereo channel separation.

Abstract: A method for providing multiple users with voice-to-remaining audio (VRA) adjustment capability includes receiving at a first decoder a voice signal and a remaining audio signal and simultaneously receiving at a second decoder, the voice signal and the remaining audio signal, wherein the voice signal and the remaining audio signal are received separately; and separately adjusting by each of the decoders, the separately received voice and remaining audio signals.

Abstract: A digital FM signal generator allows the generation of a modulated FM signal for broadcasting without the need for an analog modulator. The signal generator includes a digital signal processor which receives left and right signals from left and right signal channels and interpolates the signals to create a composite base band signal. The composite base band signal is then used by a numerically controlled oscillator to modulate a digital carrier signal. The result is a digital modulated FM RF signal which is then converted to an analog signal for broadcasting.

Abstract: Audio signal samples taken at different sampling rates are synchronized. A plurality of channels of audio data are sampled at different rates and recognizable synchronization data are added to selected samples of at least one channel of the plurality of channels.

Abstract: A stereophonic audio signal processing arrangement for variably enhancing a stereo image, wherein the stereo image enhancement is reduced at high signal levels so as to reduce distortion. The arrangement is used in a stereophonic audio reproduction system for enhancing the stereo image, which system may be part of an audio-visual reproduction system.

Abstract: The invention is directed to reducing noises of a low density without causing the listener to feel a sense of incongruity. A received signal is subjected to frequency discrimination. The sound signals of the right-channel and the left-channel are separated on the basis of a channel separation, and then are output as sounds. When noises are not generated, the channel separation is controlled in accordance with a control voltage corresponding to the electric field strength of the received signal which is output from an S-meter circuit via a channel separation controlling circuits. When noise signal in the received signal are extracted by a multipath detector, the first and the second integration circuits integrate the noise signal. When the noise density is so low that only the first integration circuit reaches the on-voltage, the channel separation is lowered to about 10 dB in accordance with the control voltage corresponding to the noise density of the channel separation controlling circuit.

Abstract: In the case of a switching arrangement for mobile radio receivers having a device for adjusting the stereo playback portion relative to the mono playback portion as a function of multipath effects, the resetting time of mono to stereo playback is a function of the relative frequency, intensity and length of multipath effects.

Abstract: A radio receiver in which, even with large variability in the components, the receiving conditions can be set according to the antenna input level in a uniform way. A high frequency cutoff circuit 30 reduces high frequency components in a composite signal by a high frequency cutoff ratio depending on a voltage applied to an HCC pin 30a. A principal signal included in the composite signal is demodulated by a principal signal demodulator 32, and a subsidiary signal is demodulated by a subsidiary signal demodulator 34. In the subsidiary signal demodulator 34, based on a voltage applied to a SPC pin 34a, the subsidiary signal demodulation level is varied from 0 to 100% according to stereo separation characteristics, to control the stereo separation. A matrix circuit 36 regenerates left and right channel signals from the demodulated principal signal and subsidiary signal. A microprocessor 20 inputs a signal meter output voltage from an FM detector IC 12.

Abstract: A system and method are provided for reducing perceived distortion in an output audio signal derived from an amplitude modulated compatible digital broadcast signal having a monophonic portion and a stereo portion. The stereo portion of this signal is demodulated to produce a demodulated stereo signal and the monophonic portion of the signal is demodulated to produce a demodulated monophonic signal. The noise in the demodulated stereo signal is measured and an estimate of the signal-to-noise ratio is derived. This estimated signal-to-noise ratio is compared with a threshold level which is set at the minimum acceptable signal quality for the stereo signal. Based upon the estimated signal-to-noise ratio, a switch directs either the monophonic derived audio output or the stereo derived audio output as the system output signal.

Abstract: A multipath interference reduction system and method for smoothly reducing noise associated with FM stereo signal reception with an adjustable blend. The system includes a peak detector for detecting noise present in the received signal. When the detected noise exceeds a first threshold limit, stereo separation reduction is provided. The amount of stereo separation reduction may be adjusted so as to provide a greater reduction at higher noise frequencies than at lower noise frequencies to enhance the audio sound. When the determined noise exceeds a second higher threshold limit, stereo separation is further reduced to provide primarily monoaural reception.

Abstract: A control for an FM receiver reduces multipath distortion by reducing stereo separation and high frequency response in the demultiplexed signal. The receiver includes an FM detector including a noise detector as well as the signal strength meter for introducing control signals to a separation control and a frequency response control. Unlike the direct input from a noise detector output to the separation and frequency response controls in the prior art, the noise detector output is input through a noise detection manager that generates responses to at least one, and preferably two thresholds of noise detector output. In the preferred embodiment, a stereo separation manager responds to a first threshold of noise and a frequency response manager responds to the second threshold. The frequency response control reduces the high frequency output at the stereo decoder or the audio processor.

Abstract: A radio receiver is provided having digital signal processing, a first and a second auxiliary signal derived from a received stereo multiplex signal, the first auxiliary signal being dependent upon the existence of signal components, whose frequency lies above the fundamental frequency range of the stereo multiplex signal, and the second auxiliary signal being dependent upon the symmetry of the sidebands of the stereo subcarrier. The first and the second auxiliary signal are combined to form an interference signal indicating the existence of interference. At least one control signal is derived from the interference signal to influence the audio signals acquired by decoding the stereo multiplex signal.

Abstract: The circuit arrangement includes a first low-pass filter (2) for filtering an input signal (H3) proportional to the strength of a received radio signal; a second low-pass filter (3) for filtering the input signal (H3); a first weighting circuit (7) for weighting the first low-pass filter output signal with first coefficients to form a first weighted output signal; a circuit device for forming a masking signal for reducing stereo channel isolation from the first weighted output signal; a second weighting circuit (5) for forming a second weighted output signal weighted with second coefficients from the first low-pass filter output signal or the second low-pass filter output signal according to a switching signal (DD2) indicative of interference in the audio signals; a switch device (4) for selecting the first low-pass filter output signal for weighting in the second weighting circuit means (5) when no interference is indicated by the switching signal (DD2) and the second low-pass filter output signal for weight

Abstract: In a radio receiver with digital signal processing, a stereo multiplex signal received and the useful signals derived therefrom are processed in digital form at a first sampling rate. The subsidiary signals derived from the stereo multiplex signal are at least partly processed at a second sampling rate that is smaller than the first sampling rate. The sampling rate of the processed subsidiary signals are reduced to the first sampling rate with the processed subsidiary signals, acting as control signals with the first sampling rate, affecting the stereo multiplex signal and the useful signals.

Abstract: A circuit arrangement for converting of a stereo signal having a mid-plane signal and a side signal into an output signal for each of two audio signal channels. By this circuit arrangement, a simplified and also automatic crosstalk cancellation is possible.

Abstract: A level detector is provided for detecting the level of a signal demodulated by a detector of a stereophonic radio receiver. A separation controller is provided for producing a separation control signal dependent on the detected level. In response to the separation control signal, a stereo decoder controls the separation of left and right channels in such a manner that the separation is increased when the detected level of the demodulated signal is higher than a predetermined level.

Abstract: A noise control system for a FM stereo receiver senses the presence of noise outside of the FM stereo transmission bandwidth at an output of a FM detector and uses variations of amplitude of the sensed noise to control stereo channel separation and audio bandwidth control circuits of a stereo decoder circuit of the stereo receiver.

Abstract: An FM audio signal receiver having a characteristic control function includes a receiving circuit for receiving an FM broadcast wave, a received state analyzing circuit for analyzing a state of the FM broadcast signal received by the receiving circuit, an analog-to-digital converter for analog-to-digital converting the FM broadcast signal received by the receiving circuit, a digital signal processor for performing processing for improving characteristics of the digital-to-analog converted signal, a parameter table memory for storing parameters for the digital signal processor and a control circuit for reading out a proper parameter for realizing improvement of a characteristic of the digital-to-analog converted signal from the parameter table memory in response to result of analysis by the received state analyzing circuit and controlling the digital signal processor with the read out parameter.

Abstract: When a stereophonic broadcasting signal is interrupted because an electric field has weakened, a pilot signal 1 which designates that the electric field is not strong enough to separate an R-channel signal and an L-channel signal from a signal received by the tuner, is also interrupted. This interruption of the pilot signal changes gains and/or phases which act on an R-channel signal and/or an L-channel signal which are applied to a sound field calibrating system.

Abstract: An FM stereophonic receiver including an FM detector circuit for detecting an intermediate frequency signal, and for providing a main signal and a sub signal in response to the detected intermediate frequency signal, a first high cut circuit, connected to receive the main signal, for providing a first high cut signal, a high cut control circuit for providing a high cut control signal in accordance with a received signal field strength level, the first high cut circuit controlling a frequency characteristic of the main signal in accordance with the high cut control signal, a second high cut circuit for providing a second high cut signal, a separation control circuit for providing a separation control signal in accordance with the received signal field strength level, the second high cut circuit controlling a frequency characteristic of the sub signal in accordance with the separation control signal, and a stereophonic demodulation circuit for providing separated right and left channel signals.

Abstract: A noise reducing circuit for reducing various noise in the output of a receiver. A noise attenuating circuit receives a demodulated signal and attenuates the noise in the demodulated signal in accordance with a control signal supplied thereto. A signal strength detecting circuit outputs a field intensity signal indicative of a strength of a radio wave signal inputted to the receiver. An output noise level detecting circuit outputs a noise level signal indicative of a noise level in the demodulated signal after the noise is attenuated. A fuzzy inferring circuit performs fuzzy inference in accordance with fuzzy production rules given by membership functions for the field intensity signal and the noise level signal, respectively so as to output an inference output. A control signal generating circuit produces the control signal on the basis of the inference output to control the noise attenuating circuit.

Abstract: A peak value detecting circuit has a peak voltage holding circuit, a voltage comparing section, a holding voltage control circuit, and a signal output circuit. The peak voltage holding circuit holds a peak value of an input signal voltage. The voltage comparing section compares the peak voltage held by the peak voltage holding circuit with an externally input signal voltage. The holding voltage control circuit controls the level of the peak voltage in accordance with the output given by the voltage comparing section as a result of the compare operation in the latter. The signal output circuit acts as a buffer in sending to the outside the peak voltage held by the peak voltage holding circuit. The output voltage from the signal output circuit is fed back as a reference voltage to a compare input terminal of the voltage comparing section and prevents any offset that may develop in the signal output circuit from appearing in the output signal voltage of the peak value detecting circuit.

Abstract: A mixed simulcast circuit in which the voice signal demodulated in the voice demodulator through the tuner and the voice signal from the outside can be recorded on the recording medium according to the user's desire, then reproduced selectively. The mixed simulcast circuit has first means for recording a signal which is received in the tuner and demodulated in the demodulator, second means for recording the modulated voice signal on the one channel of the recording medium and for recording the voice signal from the external on the other channel thereof, and means for switching selectively one signal, either the voice signal which is demodulated and recorded from tuner or the voice signal, which is recorded from the external, when it reproduced.

Abstract: The stereo separation provided by a radio receiver is controlled in dependence on the radio frequency environment at the receiver antenna. The blend curve for determining stereo separation in dependence on the field intensity of a received signal is dynamically shifted to maintain the average magnitude of a blend control signal at a predetermined magnitude if the field intensity is above a threshold. Otherwise the blend control signal follows a lower limit blend curve of predetermined shape.

Abstract: A noise component is extracted either from FM-detected output or from the so-called signal meter in the intermediate frequency amplifier. The noise component is amplified and rectified to provide a d-c signal indicative of the noise level. The rectified noise is then shaped to produce a control signal having a predetermined level and a width. The control signal is supplied to the gate circuit to control the opening and closing of the gate through which the FM detected output passes. The gate is closed during a period when the pulse noise is superimposed on the FM detected output, and is opened during a period when the pulse noise is not superimposed to the FM detected output. In the mean time, the rectified d-c signal is smoothed out to be used as a control signal for controlling the stereo separation, the attenuation of high frequency component of the MPX-demodulated audio outputs, and the overall signal level of the audio outputs.

Abstract: An FM stereo decoding and separating circuit has an (AM) demodulator multiplier to which is connected the FM stereo composite signal and a signal of dominant frequency equal to and in phase (0.degree.) with respect to the pilot signal for retrieving the L-R signal from the composite signal. This demodulator also has a blend control circuit for diminishing the magnitude of the L-R signal as a function of a blend control voltage that may be applied to the input of the blend control circuit. The decoding circuit also includes a special multiplier to which is connected the FM stereo composite signal and a signal of dominant frequency equal to that of the 38 KHz subcarrier but shifted 90.degree.

Abstract: Levels of a stereo sum signal and a stereo difference signal are detected by first and second level detectors (7, 9), respectively. Outputs of the first and second level detectors (7, 9) are compared with each other by a comparator (10). A voltage controlled amplifier (4) is responsive to an output of the comparator (10) for changing a level of the stereo difference signal, when a broadcasting signal including only either one of a left stereo signal and a right stereo signal is received, such that the levels of the stereo sums signal and the stereo difference signal are equal to each other.

Abstract: An attenuator in the composite L-R signal path used for dynamic signal control for blend purposes is limited in range by a static separation adjust signal which attenuates the maximum L-R signal to a value selected for the best right and left channel separation upon matrixing of the L+R and L-R signals. The gain of the L-R signal path is set greater than the L+R path so that a wide adjustment range is available to the separation adjustment circuit.

Abstract: A circuit is provided which gauges the amount of significant high-frequency spectral energy in the very recent history of the program material and ignores the effects of short noise bursts and other transients associated with FM reception in the moving vehicle. The circuit provides an output voltage which can be used to adjust the attack characteristics of an audio processor.

Abstract: A plastic grocery bag is provided with a tear-off coupon. The coupon is configured with the rest of the bag for rapid production and easy detachment from the bag. The plastic bag is fabricated from tubes of blown plastic. The tube is first collapsed and printed and thereafter folded at the side edges to form two "W" shaped folds along the bag sides. These folds permit the bag, when expanded, to accommodate the required containment volume. As a next step, the folded tube is both heat-sealed and cut to form sealed incremental folded tubes. These tubes are in turn cut at the bottom to form the bottom of the bag and at the top to form the paired handles on either side of an opening, which handles are characteristic of the T-shirt bag. Centrally of the top of the two handles, and for the purpose of holding a group of such bags together, there is configured on the forward wall and rearward wall of each bag a tab.

Abstract: A closed-loop attenuator for an FM stereo receiver provides attenuation to the L+R audio signal in a controlled and predictable reaction to an ultrasonic noise (USN) voltage presented to an input amplifier. This is accomplished through a closed-loop circuit configuration including a multiplier which modulates the current output of the input amplifier in accordance with the output of a master differential amplifier and supplies the modulated current to a gain stage connected to the input of the master differential amplifier. The output of the master amplifier is mirrored by a slave differential amplifier which applies the actual audio signal attenuation. The closed-loop configuration confines this linear control action to a very narrow range. Outside of this range, the circuit provides either full attenuation or no attenuation.

Abstract: Arrangement for decoding a stereo multiplex signal, having a baseband stero signal (L+R), a stereo difference signal (L-R) which is amplitude-modulated on a suppressed sub-carrier, and a pilot signal having a frequency located between the frequency bands of the two signals, the arrangement having an input for the stereo multiplex signal and left and right stereo signal outputs, the input being coupled both, via a pilot selection circuit, to a phase-locked loop for regenerating the sub-carrier and to a multiplier circuit for multiplying at least the modulated stereo difference signal by the regenerated sub-carrier. In order to improve the stereo channel separation, the pilot selection circuit includes a bandpass filter of the switched capacitor type, a clock input of which is coupled to an output of an voltage-controlled oscillator incorporated in the loop.

Abstract: An FM stereo receiver includes a level detecting circuit for detecting the received electric field intensity and a pseudo stereo circuit for changing the phase of an entered signal and outputting two signals different in phase. When the level detecting circuit detects a received electric field intensity below a threshold level, monaural signals produced from outputs of a stereo demodulator are applied to the pseudo stereo circuit to produce pseudo stereo signals.

Abstract: A decoder for use in an FM stereo broadcasting system in which the usual difference signal S and a compressed version S' of the difference signal are transmitted, automatically selects on a continuous basis for de-matrixing with the received sum signal M either an attenuated signal S' or the usual difference signal S based on the protocol that the attenuated signal S' is always selected unless the usual difference signal S is higher in level than a predetermined threshold potential related to the signal level at the knee of the expansion characteristic. The decoder eliminates the need for the relatively expensive analog variable gain amplifier used in prior art decoders and is less sensitive to time constant errors and errors due to multipath distortions.