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.

Optimum Pre-Emphasis and De-Emphasis Networks for Transmission of Television by PCM

Abstract: The advantages attendant to the use of pre-emphasis and de-emphasis networks in a PCM television system are examined. The optimum pre-emphasis network is obtained by maximizing the ratio of peak-peak signal to rms weighted noise with the coder input constrained to prevent overload. The results show that for a system using a 12-Mc sampling rate the weighted quantizing noise in the video band can be reduced about 3.7 dB, which corresponds to adding half a digit. This particular figure is based on the assumptions that quantizing noise is subjectively equivalent to thermal noise and that we have a reasonable estimate of the video signal spectrum. Networks approximating the optimum pre-emphasis and de-emphasis networks have been constructed and the performance with these networks compared to that without pre-emphasis (and de-emphasis). A visual comparison of the received pictures shows the improvement, particularly in breaking up contours.

Perceptual coding of audio signals employing envelope uncertainty

Abstract: Perceptual coding is accomplished by measuring the envelope roughness of the filtered audio signal, which may be directly converted to the noise to mask threshold needed to calculate the perceptual threshold or “just noticeable difference”. Thus, the present invention does not require any complex calculations to determine tonality, either by a measure of predictability or by the calculation of a loudness or loudness uncertainty. Instead, the envelope roughness of the signal is simply reduced directly to the noise to mask ratio.

Noise reduction scheme for a computer system

Abstract: A noise reduction scheme is incorporated into a computer system for reducing environmental background noise when a user is listening to audio output through a standard set of headphones. The noise reduction scheme utilizes the processing power of the computer system as well as built-in components of the computer for enhancing the audio quality heard by the user. Environmental background noise is received by a built-in microphone, wherein a reciprocal noise canceling signal is generated by the computer's microprocessor. The reciprocal noise canceling signal is then mixed with audio from the computer system for reducing the environmental background noise heard by a user.

Measuring noise correlation for improved video denoising

Abstract: The vast majority of previous work in noise reduction for visual media has assumed uncorrelated, white, noise sources. In practice this is almost always violated by real media. Film grain noise is never white, and this paper highlights that the same applies to almost all consumer video content. We therefore present an algorithm for measuring the spatial and temporal spectral density of noise in archived video content, be it consumer digital camera or film orginated. As an example of how this information can be used for video denoising, the spectral density is then used for spatio-temporal noise reduction in the Fourier frequency domain. Results show improved performance for noise reduction in an easily pipelined system.

Some Determinants of Interaural Phase Effects

Abstract: Recently the binaural masked threshold has been shown to depend upon the phase angle between the two ears for both the masked signal and the masking signal. These interaural phase effects are particularly clear for pure tones of fairly low frequency (100–800 c.p.s.) that are masked by white noise. It has been shown that a pure tone, in‐phase at the two ears, that is presented against a background of white noise is more easily heard when the noise is out‐of‐phase than when the noise is in‐phase at the ears. The converse is also true, namely, that if the tone is out‐of‐phase it is more easily heard when the noise is in‐phase. The masked threshold of a 250‐cycle tone presented against a background of noise (100 db SPL in a 7000‐cycle low pass band) is approximately 15 db lower under antiphasic (tone‐in, noise‐out or tone‐out, noise‐in) than under homophasic (tone‐in, noise‐in or tone‐out, noise‐out) conditions. When the same tone is masked by another tone whose frequency is fairly close but not close enough to produce beats, no such differences appear. These two masking signals represent the extremes of a continuum of complexity along which the necessary characteristics of the adequate stimulus for these differences should appear. The present experiment constitutes an attempt to find these characteristics. A pure tone at 250 c.p.s. was used as the signal to be masked throughout the experiment. Four different kinds of masking signals were used: pure tones; ‘regular’ pulses (125 p.p.s.), ‘random’ pulses (average 125 p.p.s.) and random noise. The signals were presented in frequency‐bands which were varied in respect of band‐width and center frequency. The results indicate that a regular, periodic masking signal will not produce these interaural phase effects. A necessary condition is randomness or irregularity with respect to time but not necessarily with respect to amplitude. Frequency spectrum does not enter on any such all‐or‐none basis but rather contributes to the magnitude of the response. The nearer a frequency‐band is to the frequency of the masked tone, the greater are the differences between the homophasic and antiphasic conditions. There is no substantial difference between the interaural phase effects produced by a narrow versus a wide band, provided that both bands contain the frequency of the masked tone.