# CD quality bitrate

Question 1: Here are two facts that I know about CD quality audio:

1. Audio is sampled to 16 bits at a rate of 44.1 kHz
2. The bitrate is 1411 kbps.

I can't quite work out the math.

$$\frac{16\ \text{bits}}{} \times \frac{44.1 k}{sec} = \frac{705.6\ \text{kbits}}{sec}$$

which does not equal 1411 kbps. Why?

Question 2: I remember my EE professor telling me that 44.1 kHz is the highest frequency that humans can hear. Why, then, do some online music services offer "high resolution" streams or files that are recorded at 96 kHz or even 192 kHz? Can only people with mutant-level hearing take advantage of those sampling rates?

• Are you sure you're seeing "96 kHz" and "192 kHz"? Far more likely is 96 kbps and 192 kpbs (kilobits per second) since these are common AAC/MP3 encoding bitrates. Commented May 7, 2021 at 23:37
• @EricTowers: Look at this offer page from the Qobuz music streaming service. It clearly says: FLAC 24-Bit up to 192 kHz. qobuz.com/us-en/music/streaming/offers . Also Amazon Music HD: Up to 24-bit / 192 kHz amazon.com/music/unlimited/why-hd Commented May 7, 2021 at 23:50
• These are both marketing copy. I'm fairly jaded about the technical accuracy of marketing copy. For instance, I clearly recall ads for computers having 0.064 bits of memory. ("64 mb".) Maybe this is an analog sampling rate, but I would bet a quarter it's the codec bitrate. Commented May 7, 2021 at 23:57
• @EricTowers: Here's a Sony DAC that Supports PCM 32bit/768 kHz electronics.sony.com/audio/audio-components-turntables/… Commented May 8, 2021 at 0:15
• @EricTowers we are pretty sure we are talking about 96 kHz and 192 kHz PCM streams, at up to 24 or 32 bits per sample. No codecs involved. Commented May 8, 2021 at 13:06

What is missing from your calculations is that it requires a multiplier of two because CD quality audio is two channels for stereo. 2 * 44.1 kHz * 16 = 1411.2 kbps