Will low output volume affect the quality of the sound?

Question

I recently bought a new pair of headphones and am currently using them on a Windows computer. I have connected the headphones directly to the built-in sound card of the computer and therefore I am using Windows volume controls to adjust the volume.

Since the headphones are quite "sensitive" I have to use a rather low volume and this got me thinking...

How does software controlled volume affect the quality of the output? Well, I guess there must be some reduction in quality of course, but is it 1:1 related to the selected volume?

Lets assume that my sound card is set to 16 bit 44.1 kHz quality. If I set the volume to 50%, will that reduce the bit-depth to 15 bit and will 25% reduce it to 14 bit etc.?

Answer 1

You are right!

The quality of the audio will be decreased if the volume lowered by software means. As you have correctly assumed, reducing volume in software is actually similar to reducing the bit depth.

Generally, every 6 dB of attenuation is equivalent to reducing the bit depth by one.

Brief explanation: Max volume level of your sound card output, can be considered as multiplied by 1. If the volume reduced, the signal is actually being multiplied by numbers less than one, which is causing the signal to be represented by less quantization levels (which is again - same as saying reduced bit depth).

Much better answer is provided here, including this link to a very helpful "Digital vs. Analog Volume Controls" comparison.