EchoFilter

EchoFilter was originally developed as a general-purpose real-time digital audio filter EchoFilter was designed in the first place as a multi-purpose real-time digital audio filter. It was mainly intended for radio HAMS and this latest version should be even more helpful to them. But EchoFilter 3 can be used in many more applications, and the list is growing fast.

Here are some key features of "EchoFilter":
Adjustable maximum audible frequency range up to 16 kHz (32 KHz sampling rate)
Ultra sharp digital filter down to 20 Hz. High pas, low pas, band pass and stop band filters. Non-technical and extremely easy to use.
Spectrum analyzer with adjustable resolution with virtual scrollable display. Maximum resolution is 7 Hz.
Dominant frequency readout for a 7 Hz resolution frequency counter.
Spectrogram with same resolution as the spectrum analyzer. Configurable color palette with continues color gradient for a very smooth display. Spectrogram can be scrolled horizontally for about 6000 pixels and vertically to 2200 pixels.
Time averaging (smoothing) of spectrum for detection of weak signals.
Adjustable automatic gain control of input signal.
Real-time frequency shifting (spectral shifting). Make very low and high frequencies hearable.
Real-time audio compressor and expander with adjustable threshold and gain.
Graphic equalizer. Also functions as a series of adjustable band filters.
Adjustable spectrum and spectrogram windows. Slide one of them away to turn EchoFilter into a spectrum analyzer or spectrogram only application.
Wave file recorder and player.
Noise reduction filters.
Single file 32-bit application.


Requirements:
Pentium II or better. For best performance a Pentium III is required.
64 MB RAM or more. The application can request up to 30 MB of RAM when started up.
Screen resolution of 800x600. A resolution of 1024X768 on a Pentium III will give excellent visual results. The application will NOT resize to a 640x480 resolution.
Any decent sound card with full duplex driver. All modern soundcards will give good results for general use. Full duplex refers to the ability to record and play simultaneously. Older soundcard may require a latest software driver to enable full duplex operation.
Soundcard speaker, if required.
The necessary cables to connect the soundcard to the device that generates to audio signal to be analyzed.


Limitations:
The program will run for 5 minutes, thereafter it must be restarted again. When the 5 minutes is up, the program will stop decoding data and will flash the word Demo in the status area.
The spectrogram will only display 30 seconds of data instead of the normal 8 minutes.
The sound recorder will only record 10 seconds of audio to a file.