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46-413: The High Com (also as HIGH COM , both written with a thin space) noise reduction system was developed by Telefunken , Germany, in the 1970s as a high quality high compression analogue compander for audio recordings. The idea of a compander for consumer devices was based on studies of a fixed two- band compander by Jürgen Wermuth of AEG-Telefunken ELA, Wolfenbüttel , developer of

92-663: A de-emphasis process applied at playback. Systems include the professional systems Dolby A and Dolby SR by Dolby Laboratories , dbx Professional and dbx Type I by dbx , Donald Aldous' EMT NoiseBX, Burwen Noise Eliminator  [ it ] , Telefunken 's telcom c4  [ de ] and MXR Innovations' MXR as well as the consumer systems Dolby NR , Dolby B , Dolby C and Dolby S , dbx Type II , Telefunken's High Com and Nakamichi 's High-Com II , Toshiba 's (Aurex AD-4) adres  [ ja ] , JVC 's ANRS  [ ja ] and Super ANRS , Fisher / Sanyo 's Super D , SNRS , and

138-400: A de-emphasis process applied during playback. Modern digital sound recordings no longer need to worry about tape hiss so analog-style noise reduction systems are not necessary. However, an interesting twist is that dither systems actually add noise to a signal to improve its quality. Dual-ended compander noise reduction systems have a pre-emphasis process applied during recording and then

184-521: A decoder. The Telefunken High Com integrated circuit U401BR could be utilized to work as a mostly Dolby B –compatible compander as well. In various late-generation High Com tape decks the Dolby-B emulating D NR Expander functionality worked not only for playback, but, as an undocumented feature, also during recording. dbx was a competing analog noise reduction system developed by David E. Blackmer , founder of Dbx, Inc. It used

230-418: A device's mechanism or signal processing algorithms . In electronic systems , a major type of noise is hiss created by random electron motion due to thermal agitation. These agitated electrons rapidly add and subtract from the output signal and thus create detectable noise . In the case of photographic film and magnetic tape , noise (both visible and audible) is introduced due to the grain structure of

276-529: A greater or lesser degree. The local signal-and-noise orthogonalization algorithm can be used to avoid changes to the signals. Noise reduction techniques in Digital Signal Processing (DSP) are essential for improving the quality of signals in various applications, including audio processing, telecommunications, and biomedical engineering. Noise, which is unwanted random variation in signals, can degrade signal clarity and accuracy. DSP offers

322-500: A range of algorithms to reduce noise while preserving the integrity of the original signal. Spectral subtraction is one of the simplest and most widely used noise reduction techniques, especially in speech processing. It works by estimating the power spectrum of the noise during silent periods and subtracting this noise spectrum from the noisy signal. This technique assumes that noise is additive and relatively stationary. While effective, spectral subtraction can introduce "musical noise,"

368-456: A root-mean-squared (RMS) encode/decode algorithm with the noise-prone high frequencies boosted, and the entire signal fed through a 2:1 compander. dbx operated across the entire audible bandwidth and unlike Dolby B was unusable without a decoder. However, it could achieve up to 30 dB of noise reduction. Since analog video recordings use frequency modulation for the luminance part (composite video signal in direct color systems), which keeps

414-419: A type of artificial noise, if the noise spectrum estimate is inaccurate. Applications: Primarily used in audio signal processing, including mobile telephony and hearing aids. Advantages: Simple to implement and computationally efficient. Limitations: Tends to perform poorly in the presence of non-stationary noise, and can introduce artifacts. Adaptive filters are highly effective in situations where noise

460-415: A variety of sources. Further use of these images will often require that the noise be reduced either for aesthetic purposes, or for practical purposes such as computer vision . Institut f%C3%BCr Rundfunktechnik They invented or were influential in the research, development and field-testing of important standards such as ARI , RDS , VPS , DSR , DAB and DVB-T . Institut für Rundfunktechnik

506-497: Is a statistical approach to noise reduction that minimizes the mean square error between the desired signal and the actual output. This technique relies on knowledge of both the signal and noise power spectra, and it can provide optimal noise reduction if these spectra are accurately estimated. Applications: Frequently applied in image processing, audio restoration, and radar. Advantages: Provides optimal noise reduction for stationary noise. Limitations: Requires accurate estimates of

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552-575: Is an advanced noise reduction technique that uses redundancy in the signal by averaging similar patches across the signal or image. While computationally more demanding, NLM is highly effective in removing noise from images and audio signals without blurring. Applications: Applied primarily in image denoising, especially in medical imaging and photography. Advantages: Preserves details and edges in images. Limitations: Computationally intensive, often requiring hardware acceleration or approximations for real-time applications. Boosting signals in seismic data

598-530: Is concentrated about it. Yet another approach is the automatic noise limiter and noise blanker commonly found on HAM radio transceivers, CB radio transceivers, etc. Both of the aforementioned filters can be used separately, or in conjunction with each other at the same time, depending on the transceiver itself. Most digital audio workstations (DAWs) and audio editing software have one or more noise reduction functions. Images taken with digital cameras or conventional film cameras will pick up noise from

644-400: Is especially crucial for seismic imaging , inversion, and interpretation, thereby greatly improving the success rate in oil & gas exploration. The useful signal that is smeared in the ambient random noise is often neglected and thus may cause fake discontinuity of seismic events and artifacts in the final migrated image. Enhancing the useful signal while preserving edge properties of

690-592: Is frequently confused with the far more common Dolby noise-reduction system . Unlike Dolby and dbx Type I and Type II noise reduction systems, DNL and DNR are playback-only signal processing systems that do not require the source material to first be encoded. They can be used to remove background noise from any audio signal, including magnetic tape recordings and FM radio broadcasts, reducing noise by as much as 10 dB. They can also be used in conjunction with other noise reduction systems, provided that they are used prior to applying DNR to prevent DNR from causing

736-564: Is the process of removing noise from a signal . Noise reduction techniques exist for audio and images. Noise reduction algorithms may distort the signal to some degree. Noise rejection is the ability of a circuit to isolate an undesired signal component from the desired signal component, as with common-mode rejection ratio . All signal processing devices, both analog and digital , have traits that make them susceptible to noise. Noise can be random with an even frequency distribution ( white noise ), or frequency-dependent noise introduced by

782-424: Is to define a dynamic threshold for filtering noise, that is derived from the local signal, again with respect to a local time-frequency region. Everything below the threshold will be filtered, everything above the threshold, like partials of a voice or wanted noise , will be untouched. The region is typically defined by the location of the signal's instantaneous frequency, as most of the signal energy to be preserved

828-653: Is unpredictable or non-stationary. In adaptive filtering, the filter's parameters are continuously adjusted to minimize the difference between the desired signal and the actual output. The Least Mean Squares (LMS) and Recursive Least Squares (RLS) algorithms are commonly used for adaptive noise cancellation. Applications: Used in active noise-canceling headphones, biomedical devices (e.g., EEG and ECG processing), and communications. Advantages: Can adapt to changing noise environments in real-time. Limitations: Higher computational requirements, which may be challenging for real-time applications on low-power devices. Wiener filtering

874-523: The DNR (Dynamic Noise Reduction) system for backward compatibility . Consequently, second-generation tape decks with High Com incorporated a DNR expander as well, whereas in some late-generation Telefunken, ASC and Universum tape decks this even worked during recording, but was left undocumented for legal reasons. Nakamichi , one of the more than 25 licensees of the High ;Com system, supported

920-628: The Hannover development site was partially disbanded and refocused on digital technologies in 1983, this also put the High Com development to an end. The latest tape decks to come with High Com were produced in 1986. Several software decoders were developed for telcom c4 and High Com, and are considered to be implemented for High-Com II These tape decks are known to provide built-in support for High Com: Other devices can be used with an external High Com compander box. Noise reduction system Noise reduction

966-645: The High Com noise reduction system, also developed the IC U2141B for the CBS Laboratories CX noise reduction system for LP records, a system also incorporated into FMX , a noise reduction system for FM broadcasting developed by CBS. Similar to the earlier Dolby FM system in the US, a High Com FM system was evaluated in Germany between July 1979 and December 1981 by IRT . It

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1012-561: The Hungarian/East-German Ex-Ko system. In some compander systems, the compression is applied during professional media production and only the expansion is applied by the listener; for example, systems like dbx disc , High-Com II , CX 20 and UC used for vinyl recordings and Dolby FM , High Com FM and FMX used in FM radio broadcasting. The first widely used audio noise reduction technique

1058-854: The Starsonic DL ;506, as distributed by D.A.A.F. A low-cost implementation of the Telefunken High ;Com system as external compander box became available as Hobby-Com , developed by Telefunken product development and Thomsen-Elektronik for WDR , distributed by vgs  [ de ] , and promoted for do-it-yourself assembly in the popular TV series Hobbythek  [ de ] format by Jean Pütz on 7 February 1980. In 1981 and 1982, do-it-yourself High Com kits were introduced from elektor ( elektor compander / Hi-Fi-Kompander ) and G.B.C.  [ it ] Amtron ( micro line High-Com System UK 512 (W) ). The only compander available for High-Com II

1104-486: The Telefunken telcom c4  [ de ] (formally abbreviated as "TEL" in professional broadcasting) four-band audio compander for professional use. In April 1974, the resulting "RUSW-200" prototype first led to the development of a sliding two-band compander by Ernst F. Schröder of Telefunken Grundlagenlaboratorium, Hannover since July 1974. However, the finally released High Com system, which

1150-457: The compander system was integrated into an analogue IC, TFK U401B  / U401BG  / U401BR , developed by Dietrich Höppner and Kurt Hintzmann of AEG-Telefunken Halbleiterwerk  [ de ] , Heilbronn . The chip contained more than 500 transistors. With minimal changes in the external circuitry the IC could also be used to emulate a mostly Dolby B -compatible compander as in

1196-584: The development of a noise reduction system that could exceed the capabilities of the then-prevalent Dolby B-type system. However, it became apparent that a single-band compander without sliding-band technology, which was protected by Dolby patents, suffered too many audible artifacts . So, High Com was further developed into the two-band High Com II and three-band High Com III 2:1:2 systems by Werner Scholz and Ernst F. Schröder of Telefunken assisted by Harron K. Appleman of Nakamichi in 1978/1979. The two-band variant

1242-591: The improvements it was eventually not introduced commercially because of the listening artifacts it created for receivers without expander. Besides Telefunken's own CN 750 High Com compander box, other companies also offered external High Com compander boxes such as the Aiwa HR-7 and HR-50, the Rotel RN-500 and RN-1000, or the Diemme ;Sonic-distributed Aster Dawn SC 505 and

1288-468: The medium. In photographic film, the size of the grains in the film determines the film's sensitivity, more sensitive film having larger-sized grains. In magnetic tape, the larger the grains of the magnetic particles (usually ferric oxide or magnetite ), the more prone the medium is to noise. To compensate for this, larger areas of film or magnetic tape may be used to lower the noise to an acceptable level. Noise reduction algorithms tend to alter signals to

1334-645: The other noise reduction system to mistrack. One of DNR's first widespread applications was in the GM Delco car stereo systems in US GM cars introduced in 1984. It was also used in factory car stereos in Jeep vehicles in the 1980s, such as the Cherokee XJ . Today, DNR, DNL, and similar systems are most commonly encountered as a noise reduction system in microphone systems. A second class of algorithms work in

1380-399: The playback level using a 400 Hz, 0 dB, 200 nWb/m calibration tone for optimum results, and with prices in the several hundred dollars for the external Nakamichi compander box it was much too expensive to be used by many people outside the small group of audiophiles using high-end tape recorders or open-reel decks . When AEG-Telefunken struggled financially in 1981/1982 and

1426-523: The playback of phonograph records to address scratches, pops, and surface non-linearities. Single-ended dynamic range expanders like the Phase Linear Autocorrelator Noise Reduction and Dynamic Range Recovery System (Models 1000 and 4000) can reduce various noise from old recordings. Dual-ended systems (such as Dolby noise-reduction system or dbx ) have a pre-emphasis process applied during recording and then

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1472-399: The recording medium at the time of recording. Single-ended hiss reduction systems (such as DNL or DNR ) work to reduce noise as it occurs, including both before and after the recording process as well as for live broadcast applications. Single-ended surface noise reduction (such as CEDAR and the earlier SAE 5000A, Burwen TNE 7000, and Packburn 101/323/323A/323AA and 325 ) is applied to

1518-642: The seismic profiles by attenuating random noise can help reduce interpretation difficulties and misleading risks for oil and gas detection. Tape hiss is a performance-limiting issue in analog tape recording . This is related to the particle size and texture used in the magnetic emulsion that is sprayed on the recording media, and also to the relative tape velocity across the tape heads . Four types of noise reduction exist: single-ended pre-recording, single-ended hiss reduction, single-ended surface noise reduction, and codec or dual-ended systems. Single-ended pre-recording systems (such as Dolby HX Pro ), work to affect

1564-438: The signal and noise statistics, which may not always be feasible in real-world applications. Kalman filtering is a recursive algorithm that estimates the state of a dynamic system from a series of noisy measurements. While typically used for tracking and prediction, it is also applicable to noise reduction, especially for signals that can be modeled as time-varying. Kalman filtering is particularly effective in applications where

1610-666: The signal into different frequency components using a wavelet transform and then removes the noise by thresholding the wavelet coefficients. This method is effective for signals with sharp transients, like biomedical signals, because wavelet transforms can provide both time and frequency information. Applications: Commonly used in image processing, ECG and EEG signal denoising, and audio processing. Advantages: Preserves sharp signal features and offers flexibility in handling non-stationary noise. Limitations: The choice of wavelet basis and thresholding parameters significantly impacts performance, requiring careful tuning. Non-local means (NLM)

1656-427: The signal is dynamic and the noise characteristics vary over time. Applications: Used in speech enhancement, radar, and control systems. Advantages: Provides excellent performance for time-varying signals with non-stationary noise. Limitations: Requires a mathematical model of the system dynamics, which may be complex to design for certain applications. Wavelet -based denoising (or wavelet thresholding) decomposes

1702-455: The signal-to-noise ratio on tape up to 10 dB depending on the initial signal volume. When it was played back, the decoder reversed the process, in effect reducing the noise level by up to 10 dB. The Dolby B system (developed in conjunction with Henry Kloss ) was a single-band system designed for consumer products. The Dolby B system, while not as effective as Dolby A, had the advantage of remaining listenable on playback systems without

1748-438: The tape at saturation level, audio-style noise reduction is unnecessary. Dynamic noise limiter ( DNL ) is an audio noise reduction system originally introduced by Philips in 1971 for use on cassette decks . Its circuitry is also based on a single chip . It was further developed into dynamic noise reduction ( DNR ) by National Semiconductor to reduce noise levels on long-distance telephony . First sold in 1981, DNR

1794-415: The time-frequency domain using some linear or nonlinear filters that have local characteristics and are often called time-frequency filters . Noise can therefore be also removed by use of spectral editing tools, which work in this time-frequency domain, allowing local modifications without affecting nearby signal energy. This can be done manually much like in a paint program drawing pictures. Another way

1840-411: Was Nakamichi's own High-Com II unit. More than one million High Com systems were sold between 1978 and 1982. While implemented in dozens of European and Japanese consumer device models and acoustically much superior to other systems such as Dolby B , C , dbx , adres  [ ja ] or Super D , the High Com family of systems never gained a similar market penetration. This

1886-502: Was a founding member of the Hybrid Broadcast Broadband TV (HbbTV) consortium of broadcasting and Internet industry companies that established an open European standard (called HbbTV) for hybrid set-top boxes for the reception of broadcast TV and broadband multimedia applications with a single user interface. In 2020, ZDF and then other supporters indicated that they planned to withdraw from the organization, so

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1932-483: Was also considered to be adopted for AM broadcasting . It was based on the High Com broadband compander, but eventually changed to achieve 10 dB(A) only to improve compatibility with the existing base of receivers without built-in expander. The system was field-trialed in public German FM broadcasting between 1981 and 1984 and also discussed as an option to be introduced in Austria and France. However, despite

1978-466: Was caused by several factors, including the existing pre-dominance of the Dolby system, with Dolby Laboratories introducing the " good enough " Dolby C update (with up to 15 dB A-weighted improvement) in 1980 as well, and also by the fact that High Com required higher quality tape decks and tapes to work with in order to give satisfactory results. High-Com II even required calibration of

2024-410: Was developed by Ray Dolby in 1966. Intended for professional use, Dolby Type A was an encode/decode system in which the amplitude of frequencies in four bands was increased during recording (encoding), then decreased proportionately during playback (decoding). In particular, when recording quiet parts of an audio signal, the frequencies above 1 kHz would be boosted. This had the effect of increasing

2070-421: Was eventually released exclusively as Nakamichi High-Com II Noise Reduction System later in 1979, increasing the amount of noise reduction on analogue recordings and transmissions by as much as 25 dB A-weighted. While originally designed for tape recordings, Nakamichi demonstrated the usage of High Com II on LP records as well in 1979. In 1982, the same AEG-Telefunken team, who designed

2116-510: Was marketed by Telefunken since 1978, worked as a broadband 2:1:2 compander, achieving almost 15  dB of noise reduction for low and up to 20 dB RMS A-weighted for higher frequencies, reducing the noise power down to 1% while avoiding most of the acoustic problems observed with other high compression broadband companders such as EMT /NoiseBX, Burwen  [ it ] or dbx . In order to facilitate cost-effective mass-production in consumer devices such as cassette decks ,

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