grthumongous-ga:
Thank you for requesting that I provide you with the Answer to your question.
Sound volume levels are stored in several places in a typical Windows
NT computer. The usual locations are:
- in the Windows NT Registry, linked to the Volume control applet,
with individual volume level settings for each sound source type
(Wave, MIDI, Microphone, etc.)
- for computers such as laptops with AC'97 sound integrated with the
motherboard, a nonvolatile register controlled by the PC's BIOS
- for older computers with an aftermarket sound card, and some
laptops, the sound card's amplifier will have a volume-control wheel
(a potentiometer) that physically controls the output volume
The registry is not a place to visit for the uninitiated, and finding
the volume control settings in the registry is not easy. This thread
on Experts Exchange discusses some of the techniques that can help
locate the volume control settings for your specific PC:
http://www.experts-exchange.com/Operating_Systems/Q_20634257.html
In the case of the IBM Thinkpad T21, the on-board audio output volume
setting is controlled at the hardware level by the BIOS, using three
input buttons found above the keyboard: Volume Down, Volume Up, and
Mute. While the hardware sound volume can be controlled by software
(for example, IBM has a Windows keyboard mapping utility that allows
the user to map these special buttons to hot-key combinations when
using an external keyboard), IBM has chosen to specifically NOT tie
the hardware volume setting to the Windows volume setting. However,
the Mute setting IS tied to Windows' mute setting. The 'value' in this
is that the hardware volume control also affects DOS and system
sounds, so you will not have your peace suddenly shattered by a loud
noise during boot-up due to the hardware volume setting being too high
because Windows left it there.
For older sound cards (such as the original SoundBlaster), and for
older laptops from companies such as IBM and Toshiba, a cheaper
hardware volume control was implemented to work with the analog
amplifier circuits found on those sound devices. This volume control
is typically in the form of a volume control wheel mounted on a rotary
potentiometer; adjusting the wheel raised or lowered the resistance of
the potentiometer, controlling the output volume of the amplifier. On
some computers, a linear potentiometer and a slider control were used,
but the principle was the same.
One advantage to a volume control wheel or slider, is that there is no
need for a driver or firmware to control the volume; the wheel is a
physical device, so its function remains the same no matter what
operating system is running. The other advantage of a volume control
wheel is that you can turn down the volume setting even when the
computer is turned off, to prevent a nasty audio surprise the next
time you start up the computer. For most modern sound cards for
desktop PCs, a physical volume control no longer exists, as most users
now use speaker systems that have a physical volume control built into
them. It is ultimately easier to use the volume control on the speaker
set, than to reach behind a PC to find a volume control wheel on a
sound card!
It is also possible to purchase a USB volume control device, such as this:
http://www.ahernstore.com/powermate.html
The PowerMate USB volume control's driver allows you to interface
directly with Windows' own volume control settings, giving you an
easy-to-use way of tuning your volume levels to your heart's content.
I hope that this explanation helps!
Regards,
aht-ga
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