Showing papers on "Noise published in 1981"

Pitch for nonsimultaneous successive harmonics in quiet and noise

Abstract: Pitch perception was studied with respect to nonsimultaneous successive harmonics of fundamentals in quiet and noise. Stimuli consisted of three nonoverlapping sine waves each of 40‐msec duration. Pitch perception, examined by discrimination and matching, was found to correspond to spectral frequency in quiet and fundamental frequency in noise. The results suggest a pitch processor that integrates over time (synthetic mode) in noise and analyzes spectral components (analytic mode) in quiet. The findings are discussed with respect to current theories of pitch perception and auditory integrative functions. The findings are thought to be particularly relevant to analytic and synthetic modes of pitch perception.

Infants' Detection of Speech in Noise

Abstract: Localization responses to a speech phrase masked by white noise were obtained from infants 6, 12, 18, and 24 months of age and from adults. The masking noise was presented continuously from two lou...

Spectral distribution of a sampled 1st-order lowpass filtered white noise

Abstract: In the letter, the spectrum of a sampled 1st-order lowpass filtered white noise is calculated, and theoretical results are compared with measurements made on a laboratory model. In this context, the effect of undersampling appears clearly for noise bandwidths exceeding the sampling rate. This analysis contributes to the study of noise in switched capacitor networks.

Acoustic noise suppression in the context of a perceptual model

Abstract: An acoustic noise suppression algorithm has been developed which suppresses noise from speech by first filtering it into a set of signals which approximate the loudness components perceived by the auditory system. These signals are generated by passing the input stimulus waveform through a filter bank with frequency bandwidths which approximate the ear's critical bandwidths. The noise on each signal is then suppressed using spectral subtraction techniques in a domain of simulated perception. This approach to noise suppression retains the intelligibility produced by spectral subtraction methods while eliminating the accompanying musical quality.

Classroom noise alarm

Abstract: A noise alarm for use in a school classroom to detect sound exceeding a predetermined level and which actuates a two-tone audio alarm and a light-emitting diode to notify both the instructor and students when excessive noise has been detected. The noise alarm aids the instructor in preventing excessive classroom noise which can and does disrupt and destroy a given learning situation. A sensitivity control is provided to allow the instructor to determine the noise level at which the alarm will automatically respond, and time delay means are provided so the audio alarm will not sound unless excessive noise occurs twice and within a predetermined time frame. The noise alarm also provides a digital LED readout displaying how many times the audio alarm has been triggered, thus providing the instructor with a temporary record which can be used to reinforce acceptable classroom noise levels. Other controls are also provided, allowing the instructor to "erase" the count displayed or to place the noise alarm in a "hold" mode so that the alarm is temporarily disabled without disturbing any count which is currently displayed by the LED readout.

Between and within listener variability in response to CID W-22 presented in noise.

Abstract: Two studies were conducted wherein college students with normal hearing sensitivity listened to CID W-22 recordings (Technisonics Studios) mixed with white noise. Four-word discrimination scores were obtained from each listener. In one study, a speech-to-noise ratio of approximately +1 dB was used whereas +7 dB was used in the other. Large standard deviations and low correlations indicate that the use of background noise with this clinical word discrimination test is associated with a relatively large amount of response variability and unreliability. These results suggest that the performance score obtained from a single list of CID W-22 presented in noise may not be a reliable indicator of a listener's true discrimination ability and therefore clinical interpretation of a listener's performance should be made with caution.

Magnetic recording reproducing device

Abstract: PURPOSE:To get rid of a noise which is caused at the time when the pause is released, by stopping the bias oscillation when sound recording has paused. CONSTITUTION:When the pause switch 2 is closed in a sound recording state that the sound recording switch 3 has been closed, the AND gate 11 is closed, application of a high level output passing through the inverter 9 is stopped, and the transistor 12 turns off. In this way, the head plate goes back through the play-solenoid 15 which is demagnetized, and sound recording pauses. On the other hand, the line voltage is not supplied to the bias oscillation circuit 16 whose transistors 27, 28 have turned off after a regular time according to the discharge time constant of the capacitor 26 by closing the switch 2, and the circuit 16 is stopped when sound recording has paused. In the same way, when the sound recording pause is released and the recording is restarted, the restart of operation of the stopped circuit 16 is decided in accordance with the charge time constant of the capacitor 26, and since generation of a noise at the instant when the sound recording head has been pressed against the tape is prevented, no noise is recorded.

Modifying Excessive Lunchroom Noise: Omission Training with Audio Feedback and Group Contingent Reinforcement

Abstract: Partial omission training by means of audio feedback and a group reinforcement contingency were employed to reduce excessive noise in an inpatient unit for emotionally disturbed children. Occurrence and duration of noise violations above 76 decibels were assessed using electronic audio equipment. An ABAB withdrawal design was employed to evaluate intervention effects. During treatment phases, subjects received audio feedback when noise violations occurred, and were given group reinforcement contingent upon 25% reduction in the rate of these occurrences. Results showed that the treatment package decreased the frequency of noise violations and increased appropriate lunchroom behavior, but had little effect on the duration of excessive noise.

Synthetic multichannel time series for simulating underwater acoustic noise

Abstract: The paper discusses generation of synthetic multichannel digital time series based on measured directional and spectral characteristics (second-order statistics) of underwater acoustic noise. The data are intended for analyzing the performance of array signal processors. The noise is modelled as Gaussian, stationary and homogeneous. Second-order statistics are selected as representative of noise due to distant shipping, wind action and system self-noise. A multivariate autoregressive realization of the stochastic processes is obtained via the Levinson-Robinson solution of the normal Toeplitz equations. Implementation of the time series generator on an FPS AP 120B array processor is described.

Noise elimination circuit in a magnetic recording and reproducing apparatus

Abstract: In a magnetic recording and reproducing apparatus in which a frequency-modulated video signal and a frequency-modulated audio signal are frequency-multiplexed and the frequency-multiplexed signal is recorded on video tracks of a magnetic tape (1), and the recorded signal is reproduced, a noise produced in the audio signal due to video track switching in the signal reproduction is eliminated by holding the audio signal for a period of noise duration.

Lajitas Quiet Site Noise Study

Abstract: : Ambient earth noise in the 1-20 Hz band was studied at a site remote from cultural noise sources in southwest Texas. A small structure, vertical component array was deployed which was specially designed to cope with the low noise conditions at the site. In the 1-10 Hz band, the power spectra at this site were about 10 db lower than previously reported spectra at other quiet sites. The noise appears to be stationary in time and space and is characterized by two peaks at 2 and 5 Hz, of which the sources are not known. This site appears to be capable of providing source spectral information out to at least 10 Hz, provided that the appropriate instrumentation is available

Time and frequency domain noise shaping in speech coding

Abstract: We present a general framework for the coding of signals with a time-varying short-term spectrum. The total quantization distortion is minimized by a dynamic bit allocation in time and in frequency. The resulting distortion is then white noise with fixed power. Such noise, however, is not optimal perceptually when coding speech signals. Spectral and temporal noise shaping are then used to minimize the perception of noise in frequency and in time. Initial experiments at 16 kb/s demonstrate the validity of shaping the noise in time as well as in frequency.

Noise elimination circuit for reproduction of audio signals in a magnetic tape recording and reproducing apparatus

Abstract: In a magnetic recording and reproducing apparatus in which a frequency-modulated video signal and a frequency-modulated audio signal are frequency-multiplexed and the frequency-multiplexed signal is recorded on video tracks of a magnetic tape, and the recorded signal is reproduced, a noise produced in the audio signal due to video track switching in the signal reproduction is eliminated by holding the audio signal for a period of noise duration.

Detection of pure tones in quiet and in noise by infants and adults

Abstract: Detection thresholds in quiet and in noise were estimated for infants (6 months and 12 months) using the visually reinforced headturn procedure. Test stimuli were 1000‐ and 4000‐Hz pure tones, presented monaurally (TDH‐49). In the masking condition, white noise was continually present at the earphone at 63.5 dB SPL (No = 25.5 dB). An adaptive threshold estimation procedure with a 5‐dB step size was used. An adult group was run using the same protocol as used for the infant groups. Adult data agree with existing detection estimates. Detection thresholds improve with age in each condition of this experiment. The difference between infant groups is consistent at each frequency in quiet and noise. In quiet, the infants were relatively more sensitive at 4000 Hz while adults were relatively more sensitive at 1000 Hz. In noise, detection thresholds vary with frequency in the same way for all groups. Inferred bandwidths (Sm/No) are much larger for infants than adults. Age‐related differences in task performance suggest that nonsensory factors may influence these data.

Sound recording and reproducing switching circuit

Abstract: PURPOSE:To prevent the shock sound for switching, by giving priority to muting in the device where switching for compression and expansion of the noise reduction circuit and the operation of muting are performed by a three-position switch. CONSTITUTION:At the sound recording time, when the first and the second switches 1 and 2' are connected to point R, the high frequency is compressed and is output to sound recording output terminal ROUT. When this compressed recording signal is reproduced, the first and the second switches are switched to point P to return the high-band signal to the original level and the high-band noise is reduced. When the noise for switching of recording and reproducing is muted, the sound recording and reproducing switching signal from control circuit 7 is caused to pass through gate circuit G to perform such control that this sound recording and reproducing switching signal is inhibited to perform the muting operation when the sound recording and reproducing switching signal of the second switch and the muting signal are output.

The effect of airplane noise on the inhabitants of areas near Okecie Airport in warsaw

Abstract: The state of health and noise annoyance among persons living in areas near Okecie airport exposed to various intensities of noise was evaluated. Very high annoyance effects of airplane noise of intensities over 100 dB (A) were established. A connection between the airplane noise and certain ailments complained about by the inhabitants was demonstrated.

Loud speaker broadcasting device

Abstract: PURPOSE:To make automatic adjustment of sound volume according to noise level at broadcast space, by comparing the output of broadcast use microphones and the noise detecting microphone and controlling the output of the former CONSTITUTION:In a room providing together broadcast use microphones, a noise detection microphone 2 and a speaker 3, for example, a comparison circuit 4 compares the output of microphones 1, 2 If the output of the microphone 2 is greater than that of the microphone 1, the 2nd output is produced from the comparison circuit 4 to suppress the amplification factor of an amplifier A1 Conversely, if greater, the comparison circuit 4 produced the 1st output and adjusts the amplification factor of the amplifier A1 with a control circuit 5 according to the output of the microphone 2

SNR enhancement of narrowband signals in colored noise using adaptive predictors

Abstract: Use of the Linear Prediction Filter in cascade with an FFT is demonstrated as a sub-optimum realization of the optimum filter for maximization of instantaneous signal-to-rms noise power. Computer generated colored noise and sinusoidal signals are used to compare the suboptimum filter with a conventional matched filter (designed for white noise only) in terms of output SNR for cases in which the signal and noise spectra overlap. Significant improvements are seen with the LPF-FFT cascade. Four algorithms for implementing the LPF are compared for the application. Time - frequency plots are presented that graphically illustrate the filter effectiveness to extract signals masked by colored noise.

Recognition Of Thermal Images: Effects Of Scan-Line Density And Signal-To-Noise Ratio

Abstract: A series of psychophysical experiments was carried out in order to investigate the effects of scan-line density and pictorial noise upon the recognition of thermal images of military vehicles. The basic test material consisted of a series of 69 thermographs made in the field. The thermographs were displayed indoors using a flying spot scanner system with variable scan line density and variable amounts of noise added electronically in the scanning circuit. The experiments were carried out session-wise. In each session all 69 pictures were presented in random order with the same scan-line density and the same amount of noise. Subjects were asked to identify the vehicles out of 6 alternatives. Big differences are found in recognizability between the vehicles and even bigger differ-ences between different views of the same vehicle. Hot spot front views are most difficult. On the average an identification score of 70% is obtained at about 2 scan lines per meter (measured over the real objects), when no noise is added. The effect of noise is surprisingly small. In additional experiments it was found that the scores at a fixed scan-line density could hardly be affected by MTF-operations, if not pushed to the extreme. We perhaps may conclude that prediction models as well as design approach, should recognize scan-line density as the main parameter, to be considered first.

Temporal summation in the auditory system of the goldfish

Abstract: Previous investigations of temporal integration in fishes have presented conflicting results. Popper [J. Acoust. Soc. Am. 52, 596–602 (1972)] found no evidence for integration for signals between 10 and 500 ms in duration, while Offutt [J. Acoust. Soc. Am. 41, 13–19 (1967)] clearly did. Since one of the differences between these studies was the level of a noise background, we determined to measure the effect of noise on the detectability of tone pulses as a function of pulse duration. Three goldfish (Carassius auratus) were classically conditioned to detect tone pulses ranging from 2.5 to 100 ms in duration for repetition periods of 100 and 1000 msec under both ambient (unmasked) and broadband noise conditions. The threshold function of signal duration under noise showed nearly perfect integration (3 dB decrease in threshold per doubling of duration). The function under ambient conditions showed no consistent effects of signal duration, and thus no evidence for the type of integration expected from simple models [R. Plomp, J. Acoust. Soc. Am. 33, 1561–1569 (1961)]. We conclude that the presence of masking noise may account for the previous conflicting results, and that the nature of the neural processes used in signal detection by the goldfish are fundamentally different under noisy and quiet conditions. [Work supported by N.I.H. grants to R.R.F.]

Audio muting circuit

Abstract: PURPOSE:To avoid noise during search, by making 0 the audio output during search with the audio muting circuit and enabling the audio output automatically when the serach is stopped and the reception is made CONSTITUTION:The synchronizing separation output 11 from the video amplifying and synchronization separation circuit 4 is given to the synchonization identifying circuit 9 to obtain the output 12 which is at high potential when the synchronizing signal can be confirmed and at ground potential when not identified When this output 12 is fed to the switch circuit 10 and the synchronizing signal is not present, the input to the audio amplifier circuit 7 is interrupted and audio output is produced to the speaker 8 only when the synchronizing signal is present

Das Cortische Organ nach Knallbelastung durch schwere Waffen (Raster-EM-Studie)

Abstract: Guinea pigs were exposed in different angles to the noise of a 155 mm canon. The inner ears were studied by means of scanning electromicroscopy right after the exposure. Hair cell damage was never observed in the basal coils. Corresponding to the frequency and to the SPL-maxima the hair cell injuries were mainly found in the 3rd and 4th coils. These findings support the hypothesis of a frequence and SPL-related hair cell damage.

The annoyance of impulsive helicopter noise

Abstract: A total of 96 impulsive and non-impulsive sounds were rated for annoyance by 10 subjects. The signals had the same amplitude spectrum with a maximum frequency of 4.75 kHz. By changing the phase of the spectral components different levels of impulsivity were obtained. The signals had coefficients of impulsivity of 10,8, 7,9, and -0.2 respectively. Further, signals had intensity levels 89 and 95 dBA, pulse repetition rates 10 and 20 Hz, and half the signals had pink noise added at a level 12 dBA lower than the level of the sound. The significant results were: The four females and six male subjects rated the impulsive sounds respectively 3.7 dB less annoying and 2.6 dB more annoying than the non-impulsive sounds. Overall, impulsivity had no effect. The hish pulse repetition rate increased annoyance by 2.2 dB. Addition of pink noise increased annoyance of the non-impulsive sounds 1.2 dB, but decreased the annoyance of the impulsive sounds 0.5 dB.