Common IR Measurement Settings

Common IR Measurement Settings

Outlined in the the Smaart v8.5 User Guide, these are some common "go-to" settings for dual-channel IR measurements in Smart that generally work well for a variety of purposes. For a more comprehensive, informational guide to IR measurements and the required settings, either refer to the User Guide or Part 1 and Part 2 of the IR measurement guide here on the support portal.

1. Signal Type

If you are able to use Smaart's signal generator as your stimulus signal source, then period-matched pseudorandom noise is a good all-around choice for signal type. To turn on this option, open the signal generator control panel, select Pink Noise as the signal type, then tick the boxes labeled Pseudorandom and Drop IR Data Window.

2. Input Levels/Excitation Level

When using random or pseudorandom noise signals, -12 to -15 dB is a preferred input level for IR measurement in Smaart.

If you need to measure reverberation time, then your excitation level should be at least 45 dB above the background noise level for T30 or at least 35 dB above to get T20. For most other purposes, any excitation level that is comfortable above the background level should be fine.

3. FFT Size and Averaging

128K is a decent default setting for FFT size. At a 48k sampling rate, your time window will be almost 3 seconds. You'd need more than that in extremely large spaces, but it's a good fit for smaller venues. When using period-matched noise, an averaging setting of 2 is a good starting point. 8 is a good setting if you use a random signal source, and 16 is desirable if you are working in a noisier environment, with a 0% overlap for averaging.

4. Delay Time

When using period-matched noise, a delay time of 0 is okay if it isn't already set. 

If you are using a random noise source and need to find your signal pair's delay time:

• Run the IR measurement once to find the delay.
• Click the circular gray button to the right of the delay field.
• Run the measurement again.