Popping in Sub Cal Pink Noise on Mac Book Pro

[geekwithfamily]

When I play the Sub Cal. 30-80 Hz pink noise I get a clicking or popping every half second in the output signal. It only occurs when the soundcard is set to 44.1 kHz. If I change it to 48 kHz the clicking goes away. I can't hear any clicking when I play a full bandwidth pink noise signal.

I'm on a Mac Book Pro running REW under Mac OS X (the laptop is new so I haven't had a chance to buy or setup Parallels and Windows) so the only way I can connect to my RS meter is if I have 44.1 set. Any other MBP users experiencing the same thing?

I'm pretty sure the clicks will ruin any measurements I will take.

[brucek]

Did you also set the Soundcard Sample Rate pull-down in REW to 44.1Khz to match the soundcards rate in your computer?

[geekwithfamily]

yes, the soundcard sample rate in REW is the setting I'm talking about. 48 no pops, 44 pops. Also happens on my Mac Mini (PowerPC).

[brucek]

Interesting. I will ask John (REW author) to comment on this...........

[JohnM]

Strange one. The pink noise sequence is generated in blocks of 8k samples (185ms at 44.1k) and only the filter coefficients change when switching between 44.1k and 48k, so there isn't anything happening in the code at 0.5s intervals.

If the clicks only occur when generating the sub cal and not when running a sweep then you can go ahead and make measurements anyway. If you look at the captured sweep (in the Oscilloscope graph page) and there are no discontinuities or gaps in the signal then all should be OK.

[geekwithfamily]

I spotted a related thread about another user with the same problem on a Powerbook. Guess I'll have to go the Windows route.

Would the clicks screw up the soundcard calibration/characterzation? I am connecting a double male mini-plug between the line in and out on the Macbook and keep getting errors. The impulse response is crazy like a feedback loop but I don't have monitoring on.

[JohnM]

One other possibility for the clicks/pops is interference from a wireless card, try disabling the wireless connection if it is enabled.

When you say double male mini-plug is that stereo-to-stereo? Needs to be.

[geekwithfamily]

Wireless didn't make a difference.

Here's a pic of my first graph of my sub cal:


Does this seem normal? Are the clicks in there? I'm measuring a Hsu VTF-2 and Vandersteen 1c fronts. Room is 13.5 width x 7.5 height x 30.5 length (in feet). DIY bass traps in front corners.

I'll post soon about the other little glitches in the Java/Mac interface I've found workarounds for.

[brucek]

Change the graph from Linear to Logarithmic (keeping the horizontal scale at 20hz-200Hz) and change the vertical scale to 45dB-105dB and repost it.

brucek

[geekwithfamily]

Graph is updated above. Got confused with the lin/log toggle. It is smoothed to 1/3 octave.