Misleading Measurements

[yamamoto2002]

Measurement is interesting. It shows engineers' design decision. Sometimes it is trade-off.

 

Also sometimes it shows glitch. Even if the noise caused by the glitch is well below the hearing threshold, it is better to be glitch-free IMO. Here it is example of my coding bug. The periodical click noise and ultrasonic tone is below hearing threshold but the graph implies off-by-1 error in my 2x upsample program 😁

 

[yamamoto2002]

8 hours ago, pkane2001 said:

It doesn't help me if I know that someone out there can hear out past 20kHz if my hearing range is limited to 16k. I'd rather know my own thresholds than some published average or a statistical distribution from testing of some group.

 

You may be relieved to hear there is only Do, Do♯, Re and Re♯ between 16kHz to 20kHz

 

14,080Hz A    La
14,917Hz B(A♯)  La♯
15,804Hz H    Si
16,744Hz C    Do
17,739Hz C♯  Do♯
18,794Hz D    Re
19,912Hz D♯  Re♯
21,096Hz E    Mi
22,350Hz F    Fa
23,679Hz F♯  Fa♯
25,087Hz G    Sol
26,579Hz G♯   Sol♯
28,160Hz A     La

[yamamoto2002]

6 hours ago, sandyk said:

 Even a nearby DTV in Standby mode can cause this to nearby audio equipment. Note that I am not necessarily saying a marked degradation. I am basing this on personal experience using a very low noise Preamp and C.R.O.

 

Fluorescent light glow starter and refrigerator are also problematic

 

It seems it is better to avoid office chair with gas lift as well on critical audio listening 🙂

 

https://support.displaylink.com/knowledgebase/articles/738618-display-intermittently-blanking-flickering-or-los

[yamamoto2002]

17 hours ago, bluesman said:

"Each audio sample for 32-bit float files consumes 32 bits of space on a hard disk or memory, and for a 48 kHz sampling rate, this means that 32 x 48,000 = 1,536,000 bits per second are needed for 32-bit, 48 kHz files. So for 33% more storage space compared to 24-bit files, the dynamic range captured goes from 144 dB up to, essentially, infinite (over 1500 dB). [highlighting added by me to make sure you see and read it] But more importantly, audio signals above 0 dBFS are preserved in the file, rendering clipped audio a thing of the past."

 

When FTZ CPU flag is not set, On 32bit float values that contain 24bit integer PCM values,

• amplify it by +765dB and attenuate it by -765dB → original 24bit value is fully recovered  but
• amplify it by +771dB and attenuate it by -771dB → least significant bit is smashed and bit precision is reduced to 23bit
• attenuate it by -759dB and amplify it by +759dB → original 24bit value is fully recovered but
• attenuate it by -765dB and amplify it by +765dB → least significant bit is smashed and bit precision is reduced to 23bit

 

765 + 759 = 1524 dB. I think the above `over 1500 dB'  is came from here.

 

But typical old DAWs use 32bit float with FTZ CPU flag is set (to avoid very slow denormalized number computation that hampers realtime delivery of data)

and 32bit float dynamic range is reduced to 1385 dB.

 

Newer DAWs use 64bit float as a internal representation of PCM and it has about 12000 dB of dynamic range.