SPL meter Speaker Cal noise produces rapid pitch-warble / flanging ("whee, whee")

[Lolke]

Hi everyone,

I am experiencing a specific audio artifact in REW when using the SPL meter with the Speaker Cal signal. Instead of steady pink noise, the output produces a fast-pulsing pitch modulation/flanging sound that repeats like "whee, whee, whee" at a rhythm faster than once per second.

Playing a steady single sine tone or regular music through the system sounds completely fine and clean. The issue only occurs with the SPL meter calibration noise.

System setup:

• OS: Windows 11
• Output: Topping D10s DAC (USB) -> miniDSP OpenDRC-DA8
• Input: Audient iD14 interface + iSEMcon EMX7150 measurement mic

Observations and troubleshooting:

• The rhythm of the modulation is uniform and repeats sub-second.
• In REW Preferences (Java engine), devices are selected in [EXCL] mode.
• Windows audio settings and REW are both set to 48 kHz.
• Adjusting buffer settings in REW (up to 512) does not eliminate the cycling effect.
• Power-cycling the hardware resets it, but the sound returns as soon as the SPL meter calibration signal starts.

Has anyone encountered this specific pitch-warbling issue on the SPL calibration noise, and how can it be resolved?

Thanks for any insights!


Update: I tested the Generator again, and Pink Periodic and White Periodic also produce the exact same "whee, whee, whee" pitch-warble/flanging effect. Regular sine tones remain completely fine.

 

[John Mulcahy]

That's not an artefact, it's how periodic noise sounds. Periodic noise gives more stable level readings, but you can switch to random noise on the soundcard preferences by deslecting this setting:

 

[Lolke]

Ah, that explains it! I wasn't aware that the repeating nature of Periodic Noise would sound like that to the human ear.
I unchecked "Use periodic noise for SPL calibration" in the Soundcard preferences, and it immediately switched to standard random pink noise—smooth and steady without the cycling sound.

Thanks a lot for clearing that up!