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Discussion Starter #1 (Edited)
I made my own chassis ear to pinpoint a noise from my Acura MDX (I know, it's not my FJ, but the application is universal, and I will use it on my FJ if the need arises). The purpose is to locate noises that can't be replicated in the garage, ie while moving or under load, (it's not meant tell you that your cv, bearing, etc is bad, it's meant to tell you which one is bad)

My problem is a chirping noise that is rotational, as it's affected by speed, (doesn't start until 25-30mph+ and speeds up frequency with speed), it's not affected by braking or coasting in neutral. I can't tell which corner it's coming from since it's full time AWD, and unfortunately, neither can the dealership, though they did confirm hearing it (this was an unpleasant day to say the least).

Not knowing if I could make it work, I spent as little money as possible. Knowing it works, it could be improved with a wireless, Bluetooth option, or alligator clamp microphones, better software, etc.

I was trying to replicate this but for less money
Bottom-line pricing on Steelman 6600 at ToolTopia.com

Can be done for as little as $10.50 if you have a laptop already and my version records and allows you to apply filters to pinpoint noises, but I'm not sure how to listen to live feed and switch microphones easily without adding an external 4 way selector switch like this one
4 PORT 3.5mm STEREO Manual Sharing Switch AUX Audio Speaker selector way 4:1 | eBay



Parts List

- Laptop w/ 4 USB ports
(I tried it on 2 Dell Laptops with integrated sound cards, one was Conexant, the other was IDT, one had windows 10, the other was windows vista, stereo mix not enabled on either, no problems. This writeup was done using Vista and IDT HD audio, but the same basic process applies to all Windows with differences being the sound card )


- (4) USB sound cards
(got these on ebay, went with ones with short cord so I can plug them all in at once since my usb ports are real close together)

PC Desktop USB 2.0 3D Virtual Channel Audio Sound Card Adapter For Windows 7 XC | eBay



- (4) 3.5mm Lapel Microphones

HO scale Atlas Trainman flat car, 20 000 709, TTX 81133 | eBay


- (4) 3.5mm Male to Female extension cord (10ft)

10ft 3M 3.5mm Female to Male F/M Headphone Stereo Audio Extension Cable Cord exp | eBay


- Headphones
(any will do, I used ear buds)


- Masking Tape



Software

All software is free (but beware, I didn't write it, download at your own risk)

Audacity (I used it to compare, filter recordings. I have zero prior experience with this software, so I don't know how to use it that well, but will describe how I used it. More computer savvy people might know better)

Audacity®


Alis Recording Tool (used to record from 4 microphones to separate tracks simultaneously)

https://sourceforge.net/projects/alis/
 

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Discussion Starter #2 (Edited)
Step 1

Download and install software



Step 2

Label the (4) USB sound cards. Plug in the sound cards one at a time, waiting for it to be ready before plugging in the next. It should automatically install device driver/software.





Right-click the speaker icon in bottom right of taskbar > select "Recording devices". Your sound card microphones should appear when ready to use. Make note the name of each microphone/sound card so you know which one is which. (mine are "USB PnP Sound Device", see pic)





Step 3

Place microphones at each corner of the vehicle or problem area and using extension cords, connect to the microphone plug on the usb sound cards (label each microphone wire so you know which sound card is recording which corner). Tape wire to vehicle so it doesn't flap in the wind.





You may have to adjust the microphone level up or down depending on how loud the sound is you're looking for and your background noise level.
Right-click speaker in taskbar > select "Recording Devices" > Right-click the microphone > select "properties > select "Levels" tab > adjust accordingly





Step 4

- Open Alis software
- Click the "wrench" in top right to configure settings


- Under "General Properties" tab, Select "choose" to choose a directory to save the recordings


- Under "Java Sound Properties" > Other options > select "Record in WAVE format"
- Under "Java Sound Properties" > Detected Input Lines > select the USB microphones you're using (mine are "USB PnP Sound Device") and make sure the "Enabled" box is checked for each one you want to record
- Make note the Line Input ID for each microphone.


- Click green check mark to exit configuration settings.
- Click Green circle button to start recording, Red Square to stop recording

Your recording will be separated into each track by the Line Input ID you noted earlier and will be found in the folder you chose



Step 5

- Open Audacity
- Open the audio tracks by finding them in the folder you saved them in, and drag them into the audacity window. (Pop-up window will ask import method, select "Make a copy of the files before editing"
- You can now compare the sound wave for each track looking for anomalies.



As you can see, all 4 of mine look the same, so I applied a high pass filter (I played around and tried a bunch of different stuff until I could pinpoint the sound I was looking for)

Select "Effects" > Scroll down and select "High Pass Filter" > select your cutoff frequency
I chose 16k Hz w/ a 12dB rolloff



After zooming in (left-click in the range window pane of each track zooms in, right-click zooms out, make sure to zoom in the same on each track), you can see the difference on the bottom track (all have the same HP filter applied).



If I play each track individually, with the HP (16k) filter applied, I can only hear the noise I'm looking for in the bottom track. In my case, that corresponds to "4 - USB PnP Sound Device" which corresponds to the right rear corner in my case.

Now I know where to look for the problem on the car. So I'm going to replace the microphones at different spots at the right rear and check the wheel bearing, brakes, and cv, and hope it's not a diff bearing.

Hopefully this helps me and you.
 

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Discussion Starter #6
It's actually really easy (so easy, my parents could do it, lol)...to set up and record. If the location of your problem isn't obvious in the recording, then yeah, it gets complicated figuring out how to use the software to filter out unwanted noise, maybe some audiophile or computer person would know better
 
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