WAV
Waveform Audio File Format is an audio format with a .wav file extension, used by all of Valve's engines. It is required for lipsynced dialogue and looped sounds without a custom audio backend.
GoldSrc supports uncompressed 8-bit or 16-bit PCM, although lip-synched audio must be 8-bit. It supports sample rates of 11025 Hz or 22050 Hz; other sample rates can sometimes be used, but they will be resampled to 22050 Hz before playback, without any interpolation.
Source supports uncompressed 8-bit and 16-bit PCM, as well as compressed 4-bit Microsoft ADPCM (not IMA). It supports sample rates at 11025 Hz, 22050 Hz, and 44100 Hz; files at other sample rates, such as 32000 Hz and 48000 Hz, will not play.
Note:Custom audio backends, such as MetaAudio or FMOD can extend the range of supported sample rates and bit depths.
Confirm:What about 
Source 2? It definitely supports 16-bit 44.1 KHz WAVs (mono and stereo), but does it support the other formats that and support?It supposedly supports arbitrary sample rates for MP3s; is this the case for WAVs as well?
Bug:Files using the extended Broadcast Wave Format (BWF) have weird behavior in Source, and should be converted to regular WAV using FFmpeg or Audacity before use in-game. Some audio editors export as BWF automatically, such as Pro Tools and Logic Pro, and do not provide an option to export a standard WAV.
Warning:Although the WAV format specifications permit up to 32 channels in a single file, and supports surround sound, does not support WAV files with more than 2 channels!Bit rates
WAV files have a consistent bitrate depending upon their sample rate, bit depth, and channel count. The following tables indicate what bitrates files will be at supported sample rates.
Tip:Bitrate = Sample Rate * Bit Depth * Channel CountMono sounds (1 channel)
| Sample Rate | 16-bit PCM | 8-bit PCM | 4-bit ADPCM | Quality |
|---|---|---|---|---|
| 11025 Hz | 176.4 kbps | 88.2 kbps | 44.1 kbps | AM radio; used by most  sound effects
|
| 22050 Hz | 352.8 kbps | 176.4 kbps | 88.2 kbps | Max sample rate of sound effects
|
| 44100 Hz | 705.6 kbps | 352.8 kbps | 176.4 kbps | CD quality |
Stereo sounds (2 channels) (not in )
| Sample Rate | 16-bit PCM | 8-bit PCM | 4-bit ADPCM | Quality |
|---|---|---|---|---|
| 11025 Hz | 352.8 kbps | 176.4 kbps | 88.2 kbps | AM radio |
| 22050 Hz | 705.6 kbps | 352.8 kbps | 176.4 kbps | |
| 44100 Hz | 1411.2 kbps | 705.6 kbps | 352.8 kbps | CD quality |
Some games (particularly third-party ones) may support additional sample rates and bit depths, but the above sample rates are supported by all Source games.
Tip:(only in ) If lower file sizes are desired, MP3 files can also be used in some situations; see Compression (Source 1)#Audio Compression for comparisons.Bug: Source performs nearest-neighbor upsampling for sub-44100 Hz sound files. This means that certain aural content (such as the nailgun from 
Quake) may have unpleasant and potentially tinnitus-inducing or misophonia-triggering frequencies added when played back in Source if DSP is disabled or they bypass the DSP. This issue is mostly noticeable with 11025 Hz sounds, as 22050 Hz sounds tend to have enough quality to avoid this issue. Additionally, DSP tends to mask these issues, so it mostly only affects music. GoldSrc does not suffer from this issue, as it uses the system-native resampler since the SteamPipe update.