The miniDSP UMIK-1 is the perfect companion to audio analysis programs running on your tablet or even your smartphone. In this application note we will show you how to set up your UMIK-1 with the SignalScope Pro app from Faber Acoustical, running on an Apple iPad. SignalScope Pro is able to set level and frequency response readings (FFT only) from the UMIK-1 calibration data.
Please note: miniDSP cannot provide support for third-party applications or hardware. This app note shows you how to set up the miniDSP UMIK-1 to use with SignalScope Pro but other functions of the Apple iPad or the SignalScope Pro app are beyond the scope of miniDSP support.
1. Connect [Top]
Mount the UMIK-1 into the small stand supplied with it, or if you like, you can use any other microphone stand. To connect the UMIK-1 to your Apple iPad, you will need either the Lightning to USB adapter (for newer iPads with an 8-pin Lightning connector) or the Camera Connection Kit (for older iPads with a 30-pin connector). This photo shows an iPad mini connected to the UMIK-1 via the Lightning adapter:
To generate audio output from the iPad, connect a cable from the iPad headphone socket to the system being tested. On the iPad end, the cable will have a 3.5mm stereo jack, and typically the other end has a pair of RCA connectors, as shown at left in the photograph below. Alternatively, use a 3.5mm stereo to RCA adapter, as shown at right.
2. Calibrate [Top]
If you haven't already, install the SignalScope Pro program on your iPad from the App Store.
Upon opening SignalScope Pro, it will detect the presence of the connected UMIK-1 and query you for its serial number:
Enter your microphone's serial number and press OK. SignalScope Pro will fetch the calibration file from the miniDSP website and load the calibration data. Each microphone has a unique calibration file, which is why the serial number must be entered.
Then open the Configuration screen (the "gear" icon), and tap on I/O Device Configuration and then Input Channels. You will see the UMIK-1 has been selected:
To enable frequency response compensation (FRC) for the FFT display, turn on Apply FR Compensation. (Note that FRC operates on the FFT tool, but not on the Octave analyzer tool.) To see the frequency response compensation graph, click on Frequency Response Data:
3. Measure! [Top]
Tap on Sig Gen at the bottom of the screen. You can experiment with the different types of test signal here. For now, set it as shown below, adjusting the volume so that it plays through the system at a comfortable level. Ensure that the signal generator is enabled at the top right, and turn signal generation on and off with Play/Pause button (next to the Headphones label at the top left. Adjust the level with the iPad volume control and the Noise Amplitude slider, and use the Noise Pan control to send output to only one speaker.
SignalScope Pro has a number of measurement tools, selected by the icons at the bottom of the screen. We will walk through some simple examples. To start with, tap on Octave to open the real-time analyzer (RTA), and top on the Play/Pause button at the top left (next to "UMIK-1") to start the analyzer. This will generate a pink noise test signal and display the spectrum picked up by the UMIK-1. (Note that the Octave tool doesn't use the UMIK-1 frequency response calibration data.)
(If you don't want to generate the test signal but just analyze ambient noise, tap on the Sig Gen icon, disable the signal generator, then go back to the analyzer.)
The Options screen can be used to set options, such as octave or third-octave display, frequency weighting, response time, and whether or not the display scales automatically.
Go back to the signal generator and set it to generate a square wave instead of pink noise. Now tap on the Oscope icon and then the Play/Pause button to display the actual time-domain signal being picked up by the UMIK-1:
Finally, change the signal generator to generate a pure tone (sine wave). Then go to the FFT display and tap the Play/Pause button. The display will show the tone being generated as a high "spike" as well as any distortion components. (For example, if you play a 1 kHz tone, distortion components will be at 2, 3, and 4 kHz):
Note: the distortion components may include distortion from the microphone, so take care in interpreting these results.
Finally, tap on the Meter icon. This will display a powerful and accurate SPL meter with all the features of physical meter. (If you don't want to generate the test signal but simply meter ambient noise, tap on the Sig Gen icon, disable the signal generator, then go back to the Meter.)