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Topic: Audio filter

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	Adjustable Audio Filter System
		Some important filter characteristics are the steepness of the response curve slope in the transition from passband to stopband and the general stopband attenuation.
		To prevent interaction with filter circuitry, it is desirable to use a separate power rail for the power amplifier and a 12 V rail is derived for this purpose.
		Adjustment of the filter settings enables the bandwidth to be set at the minimum required to interpret the received signal whilst eliminating noise existent on unwanted sections of the audio band.
	www.qsl.net /vk5br/SwCapFilter.htm (3343 words)

	SCAF-1 Audio Filter
		My original objective was to demonstrate, to the AM community, the use of a switched capacitor filter for “brick-wall” bandlimiting of the output of an AM audio chain… in order to limit the bandwidth of the r.f.
		Using a simple home-brew white noise generator and a PC-based audio spectrum analyser… I determined that the passband of the modified SCAF-1 is flat… and the high frequency cutoff is adjustable from 1.5 kHz – 4.5 kHz… with the expected brick wall characteristic.
		This noise is particularly noticible and the filter is particularly helpful when using the Drake R-4C to listen to a weak signal, or to monitor the band when no signals are currently present.
	mysite.verizon.net /sdp2/id14.html (769 words)

	NEScaf Audio Filter Product Reviews
		I really like the ability to continuously change the filter center frequency and bandwidth and the adjustment pots for gain and default center frequency are very thoughtful.
		These days of low sunspots numbers, when N dominates the S/N ratio, it is nice to be able to narrow the audio passband and eliminate some of the N, especially if you are a CW op.
		I have the filter connected to the headphone output of the 817 and it is plenty loud.
	www.eham.net /reviews/detail/6183 (961 words)

	FCP - A Beginner's Guide to Final Cut Pro's Audio Filters
		Audio, on the other hand, is generally broken down into doing dialogue editing, voiceover, music, ambient and sound effects separately, then combining all of these disparate elements to work together synergistically during the final mix.
		Once you are able to apply the filters and set the parameters to make your clip sound the same as the finished clips, experiment with the parameter settings, key framing and stacking different multiple audio filters on each sample.
		Because the low pass filter has a fairly dramatic effect, it was muffling the voice to the point of being unusable although it did result in a nice reduction of the hum and hiss.
	www.kenstone.net /fcp_homepage/basic_audio_filter_tutoria.html (6560 words)

	Narrow band audio bandpass filter
		The advantage of this filter is a constant 20 Hz bandwidth, regardless of the resonant frequency, when peaked between 400-4000 Hz.
		The audio line-out or headphone output from a VHF/UHF scanning or communications receiver is connected to the input of the bandpass filter.
		The audio output is from pin 7 of the LM348 IC.
	www.geocities.com /icdx_australia/audio_bandpass_filter.htm (587 words)

	Digital Audio Filter Design and Implementation Utility (Site not responding. Last check: )
		Audio filter design is accomplished by graphic placement of poles and zeros on the unit circle using a mouse.
		Filters can be applied to mono 16-bit wave files, either one at a time or in batches.
		Filter coefficients can be saved as ASCII text, as a general filter or as a cascaded second-order filter.
	dcwi.com /~bmills/filter.html (189 words)

	[Prosig.com] Audio Equalisation Filter & Parametric Filtering
		When working with audio signals a common requirement is to be able to equalise, cut or boost various frequency bands.
		A shelving filter is akin to low pass and high pass filters.
		The basic component of an equalising filter is an All Pass filter used in a feedback loop.
	www.prosig.com /signal-processing/AudioEqualisationFilter.html (628 words)

	Notch and Band
		The board is held in place by using the audio filter option stand-off location between the two electrolytic capacitors.
		When I was testing the filter I used long wires connected between the Control board and the filter board with no apparent effects on performance of the filter or the K2.
		Even though this is an audio circuit, it uses a fairly high frequency clock signal so it is important that when you build the circuit you keep the LTC1059 connections as short as possible.
	www.elecraft.com /TechNotes/notch_filter_wj4p.htm (786 words)

	Audio Filter
		Once the filter had been finally adjusted, a digital multimeter was used to measure the required value and hence select the required combination of fixed value components.
		Having decided to align the filter to the frequency of my sidetone generator, I used the oscilloscope's Channel 1 input to monitor the input to the filter (from the FT707).
		Once aligned, the filter output signal had reduced to about 25 % of the maximum output voltage (which had occurred when all four poles were tuned to the same frequency).
	www.alg.demon.co.uk /radio/136/af_filter.htm (1034 words)

	MediaMonkey :: View topic - Audio Filter Support
		I was wondering if i could do some processing of the audio stream so that is was outputed in 4.0 or 4.1 using an optical cable.
		Having looked into it i found that i could use a filter called AC3Filter to convert the mp3 stream into a Dolby Digital Stream which i can then send to a DD reciever using spdif.
		The problem stems from the fact that ac3filter is a directshow filter, not a winamp plugin, so the only programs that use it are video-playing ones.
	www.mediamonkey.com /forum/viewtopic.php?t=12630&start=0&postdays=0&postorder=asc&highlight= (849 words)

	digitalFAQ.com \| Introduction to Audio Restoration (Site not responding. Last check: )
		Restoring audio primarily involves cutting away the bad portions of the audio spectrum and then compensating the remaining parts to sound good.
		This is essentially the same as the Mild audio hiss filter, but it is accomplished by carving out a large chunk of the decibel range.
		This is because no one audio filter will be able to correct all possible audio problems.
	www.digitalfaq.com /dvdguides/restoration/audio/intro.htm (676 words)

	RC AF Filters (Site not responding. Last check: )
		Building audio filters for home built popcorn receivers using discrete components for the active elements can be both fun and instructive.
		It is important to note that the formulas given for interstage RC filter data are simplistic and do not account for other factors such as parasitic, Miller effect and wiring capacitance and the frequency to gain dependence of the active device.
		I built a filter having eight poles and was very impressed with its performance during testing on 40 meters with crowded band conditions.
	www.qrp.pops.net /filter1.htm (2158 words)

	A-Weighting Filter
		The filter response is supposed to be the inverse of one of the curves of the equal loudness graph shown in Figure 1 - it is a little hard to tell which one, but this is a standard, so we shall leave it at that.
		The filter itself is passive, and the opamps are there only to buffer the input and output, and to adjust the gain so there is some correlation with reality (however slight).
		The filter as originally shown was a little off at 2.7kHz relative to 1kHz (it should be 1.3dB higher at the higher frequency), and this has been corrected.
	sound.westhost.com /project17.htm (1451 words)

	FCP - Audio in Final Cut Pro 4.0 "For The Working Editor"
		Besides the regular audio filters that were present in FCP 3.04, FCP 4.0 includes a set of Audio Units filters that you can use to adjust your audio clips.
		The Audio Outputs tab of the Sequence Settings window allows you to define the number of audio output channels that are available to tracks in your sequence via the external audio interface connected to your computer.
		When capturing audio intended to be synchronized to video from a separate source, it's important that your device-controllable audio deck be synchronized to your computer via a common video timing signal, such as a flburst generator (also referred to as house sync).
	www.kenstone.net /fcp_homepage/audio_fcp_4_editors.html (4945 words)

	AEC System Filter
		Audio that is output through channels that do not pass through AEC is not echo-canceled.
		The preceding requirements apply to all kernel-streaming audio filter graphs that incorporate capture effects that are implemented in aec.sys.
		If you want your audio hardware to work with the AEC system filter, then the hardware rendering pin must support at least one of the sample rates supported by the AEC render-out pin and the hardware capture pin must support one of the sample rates supported by the AEC capture-in pin.
	www.osronline.com /ddkx/stream/pcdesign_82av.htm (1330 words)

	Audio Filtering with the MAXQ2000 - Maxim/Dallas
		The audio data is a prerecorded message of the author saying "The pipe began to rust while new." This text was not selected randomly—it provides a decent mix of frequency components, accentuating the audible effects of simple filters (http://www.cs.columbia.edu/~hgs/audio/harvard.html).
		In either case, a filter boils down to a characteristic equation that is essentially a weighted average of some number of the past input and output values.
		When a filter is selected, the application finds the appropriate filter, reads the shift amount and number of taps, and is then ready to start filtering data.
	www.maxim-ic.com /appnotes.cfm?an_pk=3483 (2789 words)

	MacJams.com - GarageBand Tutorial: Built-in Audio Unit Effects (Site not responding. Last check: )
		Since all of the Audio Unit effects that are included with GarageBand are really audio "filters" that do one thing or another to modify the sound waves produced by your track, it is worth it to make sure we're all on the same page with respect to certain sound concepts.
		The Hi Pass filter, and several other filters we'll see, are really just filters that work very similarly to Band Pass, but are directed to a certain frequency band rather than allowing the users to select any part of the frequency spectrum for manipulation.
		Audio compressors serve the purpose of reducing the dynamic range of an audio signal so that both the low and high amplitude sound waves are "compressed" closser to a particular ideal level somewhere in between.
	www.macjams.com /article.php?story=20040329063101758 (3205 words)

	Advanced Spam and Virus Filter- Apollo Website Hosting Services
		The filter learns not only from your individual choices but the choices of all users, making it far more powerful than any filter that relies solely on a single user's choices.
		There you will log in using the domain you wish to manage and the password provided in an email to be sent once the upgrade is complete.
		Basic settings for the strength of the filter are available on the main screen under "Filtering Aggressiveness".
	www.apollohosting.com /sitetools/spamFilter.php (0 words)

	Stereophile: Ringing False: Digital Audio's Ubiquitous Filter
		A couple of years ago, when the issue of the "energy smear" caused by digital filters was red hot (it's still smoldering), I determined to address some of the controversies surrounding this issue through what I reckoned to be a rather neat experiment.
		Since the earliest days of digital audio, engineers have had to confront the issue of high-rate, low-pass filters and their possible effect on sound quality.
		Claude Shannon's sampling theorem (footnote 1), on which the whole of digital audio is based, states that the information contained within a continuous signal will be fully captured by a discrete time-sampling process provided that its amplitude is recorded at a rate at least twice that of the highest component frequency.
	www.stereophile.com /features/106ringing (1023 words)

	nwfiir audio tools
		The task for an audio equaliser is to amplify frequencies in sound according to a given power response (often referred to as magnitude spectrum or frequency response).
		The filter we are going to create for the equalisation, will not be able to adapt to all details in the measured power response.
		In the highest frequencies the filter we are going to use will not have high resolution, and probably the microphone used during measurement has poorer precision.
	www.ludd.luth.se /~torger/filter.html (8436 words)

	The Audio Fool : Audio Fidelity: Frequency Response
		In an ideal audio system, the magnitude response is a constant unity value over all audible frequencies.
		This means signal amplitude is independent of frequency, and all tones have the same output level as their input level.
		A graphic equalizer is nothing more than an audio filter with a variable magnitude response.
	blogs.msdn.com /audiofool/archive/2006/09/20/762876.aspx (629 words)

	Compassion Over Killing > Building a Faunette: Noise Filter (Modified Audio Cable)
		Although this filter provides sound to two speakers, it is actually mono doubled, not stereo.
		Six-foot, shielded audio cable for connecting audio components, ⅛-inch mono to ⅛-inch mono mini-plug.
		The idea is to keep the wires from pulling free of their soldering points and to secure the audio isolation transformer tightly to this “sound filter” cable.
	www.cok.net /lit/faunette/filter.php (561 words)

	Tusa Consulting Services (Site not responding. Last check: )
		The audio filter is an active bandpass filter whose response is 200 to 3500Hz.
		The first is to bandlimit the audio response and restrict the transmitted bandwidth to less than 4KHz.
		The audio limiter originally used mercury cells to bias the clipper diodes.
	www.tusaconsulting.com /af_filter_limiter_issues.htm (682 words)

	Easy Audio Editor, MP3 Editor, Music Editor Software - Functions List
		You can also drag the audio file from your folder and drop on the Wave View in the main window to open audio file for editing.
		Starts playback of the current selection, or of the current audio file from either the left edge of the selection, or from the beginning of the file, to either the right edge of the selection or to the end of the file.
		This allows you to analyze your audio data to see which frequencies are most prevalent.
	www.dandans.com /EasyAudioEditor_functions.htm (1632 words)

	EchoFilter - Digital Audio Filtering Software
		The latest version incorporates a powerful programmable audio filter as well as a frequency counter up to 16 kHz with a 7 Hz resolution.
		The filter bandwidth can go down to 20 Hz and can extract signals and sounds from the audio signal that may normally be close to inaudible.
		This version incorporates a programmable audio filter as well as a frequency counter up to 10 kHz with a 10 Hz resolution.
	www.computecsa.co.za /echofilter (272 words)

	Audio Phaser Filter (Site not responding. Last check: )
		The phase filter can be used to add the distinctive phaser sound.
		Notches are created by filtering the signal, and mixing the filter output with the input signal.
		Changes will be applied directly to the streaming media with the ability to set them permanently using the Apply button or abandon them by pressing the Cancel button.
	www.leadtools.com /Help/DirectShowFiltersEU/Filters/LEADAudioPhaserFilter.htm (227 words)

	Avid Community Exchange - Music Audio Filter: INT Restaurant feel
		does anyone have any suggestions for using and/or modifying an EQ filter to make a piece of music from a CD, sound like it is playing in a Restaurant.
		The best that I got was using the Telephone A filter and then bringing up the High end a little.
		Be careful with reverberation, because your voices probably should have the same reverb then.
	www.avid.com /exchange/forums/60414/ShowPost.aspx (282 words)

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