Default Audio Volume Settings

The SndVol32 program (see SysTray and SndVol32) displays a set of volume sliders. A master volume slider controls the volume of the mixed output signal. The other sliders indicate the volume-level settings for the various audio sources such as wave, CD audio, and MIDI. If the driver does not explicitly initialize these volume settings at the time that it is installed, the operating system chooses its own default values for these settings. The defaults that the operating system chooses are not the same across all Windows releases, and vendors might need to take these differences into account to ensure that the volume levels are set neither too high nor too low immediately following driver installation.

By default, Windows 2000 and Windows Me/98 set all the SndVol32 volume levels to the middle of the slider, a position that represents 6 decibels of attenuation. The operating system applies this default setting to both the master volume slider and the volume sliders for the various audio sources.

The wave, CD audio, and MIDI sliders typically control volume nodes on the KMixer system driver. These nodes scale the data in the audio stream before it reaches the audio hardware. By attenuating the data, KMixer discards digital resolution that the hardware could use to render a higher-quality audio signal.

In Windows XP and later, the operating system uses a different set of default volume settings to avoid this loss of audio quality. It sets the volume levels on the wave, CD audio, MIDI, and other audio sources to zero decibels of attenuation (pass-through mode). This translates to a full-volume slider setting for each of these sources in SndVol32. These settings improve the default sound quality by ensuring that KMixer does not degrade the original resolution of the source signal.

In Windows XP and later, the default master-volume setting remains unchanged at 6 decibels of attenuation. The master volume control represents the hardware volume node on the adapter pin to which KMixer's output pin is connected.

Of course, the INF file that installs an audio adapter driver can override the operating system's default volume settings with its own default settings. To achieve the best sound quality at installation, a driver should leave the default volume settings on the various audio sources (wave, CD audio, MIDI, and so on) at full volume and set the default master volume to 6 decibels or more of attenuation. A default master volume setting in the range 9 to 18 decibels of attenuation is typically loud enough to be clearly audible. A default setting of zero decibels (full volume) for the master volume control might subject users to an unpleasantly loud sound the first time they boot their systems following device installation.

As a general rule, if the audio adapter drives a set of analog speakers that have their own volume control, the INF file should not set the default volume level too low. Otherwise, a user might try to compensate by increasing the volume on the speakers instead of increasing the master volume on the sound card. The result of amplifying a low signal level is loss of audio quality.

Ideally, if a set of active speakers ships in the same box with the audio adapter card, the factory should adjust the volume knob on the speakers to the position that works best with the adapter's default volume setting. If the audio adapter does not have a physical volume control knob, see the Windows Vista Software Volume Control Support topic for information about the software support provided.

Note  If the audio hardware exposes a hardware volume control (like a volume knob), then the driver sets the range and the default level via the KSPROPERTY_AUDIO_VOLUMELEVEL Kernel Streaming property.

The following table shows the volume ranges and default volume levels for audio in the different versions of Windows.

Windows versionMicrophone default valuesNon-microphone* default values
Windows Vista (RTM)

Default level: 0.0db

Volume Range : -192.0db ~ +0.0db

Windows Vista SP1

Default level: 0.0db

Volume Range : -192.0 dB ~ +12.0dB

Default level: 0.0db

Volume Range : -192.0 dB ~ 0dB

Windows 7

Default level: +30.0dB

Volume Range : -192 dB ~ +30.0 dB

Default level: 0 dB

Volume Range : -192 dB ~ 0 dB

Windows 8

Default level: 0.0 dB

Volume Range: -96 dB ~ +30 dB

Default level: 0.0 dB

Volume Range: -96 dB ~ 0 dB

 

*The term non-microphone describes all playback devices and recording devices other than microphones.

For information about the operational characteristics of the physical volume sliders that are represented by the software volume sliders in Windows applications, see Audio-Tapered Volume Controls.

Related topics

Customizing Default Audio Volume Settings

 

 

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