Noise

About: Noise is a research topic. Over the lifetime, 5111 publications have been published within this topic receiving 69407 citations. The topic is also known as: Мопсы танцуют под радио бандитов из сталкера 10 часов.

Reduction of noise and bias in randomly sampled power spectra

Abstract: We consider the origin of noise and distortion in power spectral estimates of randomly sampled data, specifically velocity data measured with a burst-mode laser Doppler anemometer. The analysis guides us to new ways of reducing noise and removing spectral bias, e.g., distortions caused by modifications of the ideal Poisson sample rate caused by dead time effects and correlations between velocity and sample rate. The noise and dead time effects for finite records are shown to tend to previous results for infinite time records and ensemble averages. For finite records, we show that the measured sampling function can be used to correct the spectra for noise and dead time effects by a deconvolution process. We also describe a novel version of a power spectral estimator based on a fast slotted autocovariance algorithm.

The Noise of a Forward Swept Fan

Abstract: A forward swept fan, designated the Quiet High Speed Fan (QHSF), was tested in the NASA Glenn 9-by 15-foot Low Speed Wind Tunnel to investigate its noise reduction relative to a baseline fan of the same aerodynamic performance. The objective of the Quiet High Speed Fan was a 6 decibel reduction in the Effective Perceived Noise relative to the baseline fan at the takeoff condition. The intent of the Quiet High Speed Fan design was to provide both a multiple pure tone noise reduction from the forward sweep of the fan rotor and a rotor-stator interaction blade passing tone noise reduction from a leaned stator. The tunnel noise data indicted that the Quiet High Speed Fan was quieter than the baseline fan for a significant portion of the operating line and was 6 dB quieter near the takeoff condition. Although reductions in the multiple pure tones were observed, the vast majority of the EPNdB reduction was a result of the reduction in the blade passing tone and its harmonics. The baseline fan's blade passing tone was dominated by the rotor-strut interaction mechanism. The observed blade passing tone reduction could be the result of either the redesign of the Quiet High Speed Fan Rotor or the redesigned stator. The exact cause of this rotor-strut noise reduction, whether from the rotor or stator redesign, was not discernable from this experiment.

Noise independent speech recognition for a variety of noise types

Abstract: By a base transformation technique, we previously reported a recognizer which gives a noise-adapted recognition rate of 90% under 10 dB SNR on a vocabulary of 206 words. This rate is 97% of the recognition rate for clean speech. The technique is extended here so that the input noise is first recognized as one of a set reference noises, and the noise reference is used for the base transformation of the noisy utterance. Using 32 reference noise classes, for speech signals corrupted by noises of unknown natures (either Gaussian, bus or aircrafts with SNR randomly from 10 to 40 dB), we obtained a noise-independent recognition rate of about 95.5% of the recognition rate for clean speech. >

Method and apparatus for editing an audio signal

Abstract: An audio signal editing method and apparatus for use with original sound data which is already compressed and encoded in predictive form, for example ADPCM. To edit a desired portion from the original audio data, the method and apparatus reconstruct (encoded PCM) audio data from the original (ADPCM) audio data and encode a non-predictive unit to replace a first original audio data unit of the desired portion. Thus, the desired portion is rendered independent of preceding sample values, without having to be recoded entirely. An enhanced method and apparatus encode further replacement units to eliminate noise introduced by the basic method.