V6 exhaust sound recording

[Speedy Emira]

I have a Miltek exhaust with the third cat delete pipe and I’d like to do some sound recording comparison with a standard car.
Does anyone know the best way to record it?
I have a decent microphone used for recording training videos at work that could be used with a laptop. I have a Go Pro black and an iPhone so if any of you are YouTube content guys I’d appreciate your advice.
At the same time I intend to use a calibrated sound metre to record the levels in different modes.

 

[Porter]

You need control over the microphone level and the ability to keep it fixed. The best results will probably be from high quality standalone recorder like a Tascam or Zoom, with a wind sock. You can get a nice Tascam for under $100.

They are designed to be able to record accurately in very loud environments like a concert, which the average desktop mic for a computer is not.

 

[Eagle7]

Something like this is very difficult because there are so many variables. One of those is your own level of hearing accuracy. Have you taken a hearing test? Do both your ears have the same level of hearing ability? Sound levels, frequency levels? If you want to be as accurate as you can, start there so you have an idea of what hearing biases your ears may have.

As Porter said, you'll need to choose a mic. If you're going to use a laptop, either choose a mic that's USB compatible or you'll need an adapter. What software are you going to use to record with? You may need a mic with a pattern switch, or a roll-off switch to keep it from being over-loaded. An exhaust is loud and has a lot of strong frequencies. You can compensate with your computer software, but that won't help if the mic is over-loaded from the beginning. It will clip the sound and distort.

It's been years since I was involved with recording, but a solid standby was always a Shure SM57. It's a solid dynamic mic. They're under $100 and can handle a lot of things, even the intense dynamics of drums. You'll need an XLR to USB adapter cable which should be under $20 (these are U.S. prices). This is a workhorse mic that's been used universally both live and in the studio for decades.

You'll need to pick a recording environment. Try to find a place that's acoustically neutral so you don't get a lot of reverb or echo. Are you going to record how it sounds inside the car, outside, or both? You might want a couple of different types of stands; a floor stand, and a short tripod stand. Because of the intensity of the frequencies, try and put the mics on something that will isolate them from vibration. You can use a thick piece of foam to put the tripod stand on, and maybe something like that for the floor stand as long as you don't have it extended up too high. You don't want it to wobble or move.

Once you have your recording setup, now you have to choose how you're going to monitor it. For a laptop you'll probably use headphones. Typical retail headphones are biased towards the bass frequencies because that's what customers like, but that's not good for monitoring recordings. Ideally you'll want neutral headphones, but that can get expensive quick. Whatever headphones you use, you'll need to do some experimenting in your recording software to equalize the sound they're putting out. Compare what you hear through the mic with them on, slide them off and compare what you're hearing naturally, put them back on, etc. until you feel you've got them equalized pretty close to neutral.

A decibel meter is going to be very useful. You can use that just to see what the sound levels are straight to your ears naturally, without the mic. You'll need to use the software on your laptop to adjust the levels the mic is picking up. The nice thing about the Shure SM57 is it isn't too sensitive, so it's much less likely to get blown out and distort.

Once you have your recordings, you can make adjustments with the software to get it as close to what your ears hear naturally as you can, but keep in mind there's no way to know what the listener is going to be using to listen to it. Headphones will be different from external speakers, and there's a huge amount of difference in each of those types. Earbuds vs over the ear headphones, computer speakers vs desktop vs home theater, etc.

Whatever you use, document it. Let us know what mic you used, what the settings were on the mic if it has those, how far away and what the placement was for the mic, what software was used to record the sound, what filter settings you used in the software, etc. Tell us what the sound levels were with the DB meter before you started recording.

The things people are probably going to be interested in the most is how loud is it, what is the tone quality, and what are the frequencies. Your computer recording software should have an equalizer plug-in which will have a frequency meter. If you can, video record that meter as you're monitoring the recording to show what the frequency profile is. That will show what frequencies the exhaust is generating and how strong they are as heard through the mic.

All the above should give you a reasonably realistic representation of what the exhaust actually sounds like to someone in the car or standing outside at the location you put the mic.

I look forward to seeing what you come up with!

 

[Speedy Emira]

Well guys this is some seriously good advice. When I get to work next week I’ll get the headphones and mic and post the details to see if they are any use before buying something more suitable.
I have a great sound meter that is super accurate for all frequencies.
I didn’t think of software and intended to use the Premier Elements. I looked at the Adobe subscriptions but I would sooner pay outright which is a thing of the past.

 

[Eagle7]

Well guys this is some seriously good advice. When I get to work next week I’ll get the headphones and mic and post the details to see if they are any use before buying something more suitable.
I have a great sound meter that is super accurate for all frequencies.
I didn’t think of software and intended to use the Premier Elements. I looked at the Adobe subscriptions but I would sooner pay outright which is a thing of the past.

What computer do you use? If it's a Mac, they all come with Garageband for free, and it's very good. It doesn't have all the full features pro level recording software has, but it's no slouch. It'll do everything you need for this test. If you have a PC, I know there are some free recording programs that do a decent job, and one of them which is popular and been around awhile is Audacity.

https://www.audacityteam.org/

As for headphones, the Beyerdynamic DT-770 Pro used to be a decent choice. There may be newer phones that are better, but the Beyer wasn't too expensive and worked very well. Amazon has them for $169 and you have your choice of 3 different OHM ratings, depending on what your laptop can handle. The 32 OHM would be a safe choice. Unless you plan on making audio recording your hobby, you don't need to spend any more than this on headphones.