Audacity

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Audacity is a free, easy-to-use, multi-track audio editor and recorder for Windows, Mac OS X, GNU/Linux and other operating systems. The interface is translated into many languages. We can use Audacity to:

• Record live audio.
• Record computer playback on any Windows Vista or later machine.
• Convert tapes and records into digital recordings or CDs.
• Edit WAV, AIFF, FLAC, MP2, MP3 or Ogg Vorbis sound files.
• Cut, copy, splice or mix sounds together.
• Change the speed or pitch of a recording.

Features :

Recording :

• Device Toolbar manages multiple input and output devices.
• Level meters can monitor volume levels before, during and after recording. Clipping can be displayed in the waveform or in a label track.
• Record from microphone, line input, USB/Firewire devices and others.
• Record computer playback on Windows Vista and later by choosing "Windows WASAPI" host in Device Toolbar then a "loopback" input.
• Timer Record and Sound Activated Recording features.
• Dub over existing tracks to create multi-track recordings.
• Record at very low latencies on supported devices on Linux by using Audacity with JACK.
• Record at sample rates up to 192,000 Hz (subject to appropriate hardware and host selection). Up to 384,000 Hz is supported for appropriate high-resolution devices on Mac OS X and Linux.
• Record at 24-bit depth on Windows (using Windows WASAPI host), Mac OS X or Linux (using ALSA or JACK host).
• Record multiple channels at once (subject to appropriate hardware).
• Import and Export
• Import and export WAV, AIFF, AU, FLAC and Ogg Vorbis files.
• Fast "On-Demand" import of WAV or AIFF files (letting you start work with the files almost immediately) if read directly from source.
• Import and export all formats supported by libsndfile such as GSM 6.10, 32-bit and 64-bit float WAV and U/A-Law.
• Import MPEG audio (including MP2 and MP3 files) using libmad.
• Import raw (headerless) audio files using the "Import Raw" command.
• Create WAV or AIFF files suitable for burning to audio CD.
• Export MP3 files with the optional LAME encoder library.
• Import and export AC3, M4A/M4R (AAC) and WMA with the optional FFmpeg library (this also supports import of audio from video files).

Sound Quality :

• Supports 16-bit, 24-bit and 32-bit (floating point) samples (the latter preserves samples in excess of full scale).
• Sample rates and formats are converted using high-quality resampling and dithering.
• Tracks with different sample rates or formats are converted automatically in real time.

Editing :

• Easy editing with Cut, Copy, Paste and Delete.
• Unlimited sequential Undo (and Redo) to go back any number of steps.
• Edit and mix large numbers of tracks.
• Multiple clips are allowed per track.
• Label tracks with selectable Sync-Lock Tracks feature for keeping tracks and labels synchronized.
• Draw Tool to alter individual sample points.
• Envelope Tool to fade the volume up or down smoothly.
• Automatic Crash Recovery in the event of abnormal program termination.

Accessibility :

• Tracks and selections can be fully manipulated using the keyboard.
• Large range of keyboard shortcuts.
• Excellent support for JAWS, NVDA and other screen readers on Windows, and for VoiceOver on Mac.

Effects :

• Change the pitch without altering the tempo (or vice-versa).
• Remove static, hiss, hum or other constant background noises.
• Alter frequencies with Equalization, Bass and Treble, High/Low Pass and Notch Filter effects.
• Adjust volume with Compressor, Amplify, Normalize, Fade In/Fade Out and Adjustable Fade effects.
• Remove Vocals from suitable stereo tracks.
• Create voice-overs for podcasts or DJ sets using Auto Duck effect.
• Other built-in effects include:
  • Echo
  • Paul-stretch(extreme stretch)
  • Phaser
  • Reverb
  • Reverse
  • Truncate Silence
  • Wahwah
• Run "Chains" of effects on a project or multiple files in Batch Processing mode.

Plug-ins :

• Support for LADSPA, Nyquist, VST and Audio Unit effect plug-ins.
• Effects written in the Nyquist programming language can be easily modified in a text editor - or you can even write your own plug-in.

Analysis :

• Spectrogram view modes for visualizing frequencies.
• "Plot Spectrum" command for detailed frequency analysis.
• "Sample Data Export" for exporting a file containing amplitude values for each sample in the selection.
• Contrast Analysis for analyzing average rms volume differences between foreground speech and background music.
• Support for adding VAMP analysis plug-ins.