This VI is designed to run a short DAQ for evaluating noise levels in imaging areas. This README serves to explain how to use the VI for data acquisition and explain some of the results of the sounds caused during two-photon excitation microscopy. Laboratory animal's auditory range is significantly different than that of humans, and the (negative) effects of high-frequency noise in animal housing environments has been documented.
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| Figure 1: Auditory comparison for humans and common laboratory animals. |
See: Journal of the American Association for Laboratory Animal Science, Volume 46, Number 1, January 2007, pp. 10-13(4) by Turner (good work, but not from me) et al. https://www.ncbi.nlm.nih.gov/pubmed/17203909 and https://www.ncbi.nlm.nih.gov/pubmed/15766204 (Figure 3)
Human hearing ranges from ~ 20-20kHz, represented by the black dashed line in Figure 1. Most mammalian hearing curves represent an approximate "U" shape, with the frequencies in the center being the most sensitive; i.e. you can still hear them at a quieter volume. In most humans, this typically peaks between 2-5 kHz. Perhaps not surprisingly, this range is exactly the frequency range of a human baby crying - typically centering around 3.5 kHz.
In many other mammals, particularly those used in scientific research, have hearing ranges whose frequencies are typically shifted to the right (higher). As shown in figure 3, a laboratory mouse's hearing range extends from approximately 1 kHz to 100 kHz with sensitivity peaks around 12-25kHz. This difference in hearing range between humans and laboratory animals (particularly mice) makes it difficult to understand how imperceivable and/or inaudible high-frequency noise can be present. An otherwise silent environment for us may appear as a comparative rock concert for an animal. This issue is further exacerbated by the tendency of high-frequency hearing sensitivity to deteriorate with age. By age 40, most humans can only hear below 15 kHz. Around age 50, 12 kHz. While nearly all humans can accurately perceive up to 8 kHz, the sensitivity to high-frequencies and their perceived "volume" is highly variable.
Since our lab is interested in studying various aspects of neurovascular coupling during sleep states, it is imperitive for us to do our best to cater to the animal's hearing sensitivity. While it is beneficial that our normal talking voices, typically in the hundreds of Hz (unless singing) are likely completely inaudible to a mouse, there are a plethora of potentially high-pitch sounds from various computers, scannings mirrors, pumps, fans, and other equipment that go unnoticed. For these reasons described above, the following VI and corresponding sample data demonstrate a real-world example of these concepts during our experiments.
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| Figure 1: Auditory comparison for humans and common laboratory animals. |
| Hardware, Manufacture | Documentation | Purpose |
|---|---|---|
| Avisoft CM16/CMPA24AAf-5V | https://www.avisoft.com/usg/cm16_cmpa.htm | Condensor Microphone |
| National Instruments USB-6343 | http://www.ni.com/en-us/support/model.usb-6343.html | DAQ device |
This VI uses a few Express VIs for convenience, but unfortunately don't have a clean way of adding those controls to the front panel. On the front panel, you can adjust the time bewteen 1 and 60 seconds, and can easily increase the value by adjusting the gauge properties. A purple LED will illuminate once the microphone starts recording data, and will shut off with the illumination of a blue light when data acquisition is completed. The sampling rate can be adjusted in the Analog Fs box. Verify your specific device's maximum sampling rate. To not alias the mouse's hearing range, you need at least 200kS/s. A filepath box allows you to determine the file-save location. Each file is automatically named YYMMDD_HH_MM_SS, so each will have a unique file name regardless of duration. To change the save directory, type the filepath into the designated field.
The condensor microphone has 4 input wires - PWR (+5), GRND, and an Analog (+) and Analog (-). Nearly all NI boards have power and ground pins, and most have serveral analog input (AI) pins for analog differential recording. Consult your device's pinout for specifications.
While the acquisition duration, sampling rate, and filepath can be set-up and adjusted on the front panel, you need to tell the Express VI which device and analog pin you're connected to. To do this, you have to enter the block diagram. To do this, hit CTL+T.
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| Figure 1: Auditory comparison for humans and common laboratory animals. |
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| Figure 1: Auditory comparison for humans and common laboratory animals. |
A menu in the DAQ Assistant will pop up and give you access to the different parameters. The only parameter that you have to change is the Device/Physical Channel. You do this by right clicking the "Voltage" Channel setting and selecting Change Physical Channel. You device should be present, and you can select the correct analog channel from the drop-down menu. After selecting, click OK and then OK again at the bottom of the DAQ Assistant menu. The menu will then close, and the Block Diagram will update (temporarily breaking all the wires) and the re-assemble.
Note: You can see the Acquisition mode, samples to read, and Rate (Hz) fields. There's also a File save path option if you go exploring. You can change these, but it will not do anything. The front panel values override whatever you put in these fields. When you close the DAQ Assistant menu, you may get an error warning you that things will not work in their current state. Disregard the warning, and return to the front panel as the "errors" are corrected with the front panel's input parameters. While there is a "device name" wire terminal in the Express VI's block, you are unfortunately unable to add the actual physical channel to avoid having to actually enter the DAQ Assistant.