Recording sounds - Equipment & Methods?

Discussion in 'Car Modding' started by KingKenny04, Mar 22, 2017.

  1. KingKenny04

    KingKenny04 Registered

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    Hey all. Working on a project and I'm curious about what it takes to record engine sounds. I understand that sounds need to be taken both inside the cockpit and outside, AND out of gear and under load.

    Can anyone recommend specific equipment for this task? I don't have any sound equipment myself but I do have a few places I can rent from. Also what would the exact method be for recording these sounds? Where is the optimum placement for the mics inside and outside the car?

    My complete guess would be:

    Mic in the cockpit, another mic about 3 feet behind the exhaust tip

    Record idle for about 30 seconds. Have the driver rev up from idle about 500 rpms and hold for 30 seconds. Repeat every 500 RPMS until redline.

    Have the driver go out on track and repeat, except with the car in gear.

    Does that sound right?
     
  2. Emery

    Emery Registered

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    Ideally you need loaded on-throttle exhaust/engine noises and off-throttle, not unloaded. People with money use electric wheel dynamometers (one dyno per driven wheel) so they can run a constant rpm under load with minimal extrenous noise. Dynojets can be used, but you have to filter out the dyno's whine and/or swamp the microphone with a sound level that nearly clips. The poor people have to find steep hills and make sure the recording isn't also picking up gravel, wind, gearbox whine, etc, and go downhill in addition to uphill, using 1st or 2nd gear. If you have time, record the transmission noise separately, with the mic as close as possible so the exhaust noise is drowned out. Remember to record in stereo!

    500 rpm increments are too many. For a street car, you'd want samples at idle, 2000 rpm, 4000 rpm (or a little higher than wherever VTEC kicks in), and near redline. You also want to record a general driving sample to aid in mixing the levels in-game. Expect the mixing process to be the hardest part. There will be processing required before you mix, like ensuring the samples are not clipping and start/end at zero-crossing and you may find the need to apply filters. There are some mixing tricks, too, like working with the backfire sounds to get the correct crack, rumble, or pfft for shifts.

    External microphones should have those hairy, fuzzy wind noise mufflers on them otherwise you'll get nasty booming/rumbling wind effects. Avoid driving by walls so there are no echoes/reverb. Expect your first few recording attempts to be a learning process rather than a final product as you'll discover things you'll want to do better.

    There are few vids on YouTube with the process and Google will turn up more help. Ducfreak, over on nogripracing.com is helpful.
     
  3. KingKenny04

    KingKenny04 Registered

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    I figure I'll only really have one shot at this, since I'm renting this equipment. The cars I'm taking sounds for are oval track cars that don't ever go up or downhill. Would I still need some kind of "uphill" run?

    Also can you recommend any kind of specific recording equipment?
     
  4. Bozak

    Bozak Registered

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    Make sure that you'll use a stereo mic and a portable recorder that records at 24bit/192khz or 96khz and use the wav. file format. Check recording levels to -12db to -6db maximum input level. With digital recording you'll never want to go 0db.
    A popular recorder is Tascam DR-100MK3 which also has stereo mic attached. It also has limiter so you don't reach 0db.
     
  5. Emery

    Emery Registered

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    Marantz, Zoom, & Roland are other brands of portable recorders, some with built in microphones. When I looked into them a few years back, there was no perfect one that came out on top as each seem to sacrifice some desireable feature. It's possible they've improved since then, but I also got the impression that these companies move slowly. AVC (automatic volume control) may or may not be a good idea because you can lose the dynamic range & subtleties, however it keeps the neophyte from clipping. Multi-track with extra plug-in mics would let you record both interior and exterior and transmission sounds in one go. For exterior & transmission recording you probably want plug-in mics rather than exposing the recorder to hazards.

    If you're stuck with cars on a circle track and no dyno, then you're just going to have to figure out a way to make it work. Mainly you'll want them rolling and away from the walls. In this situation, I can't think of any way to minimize processing of the off-throttle samples as there's no way to keep the revs fairly constant.

    Edit: Here's a link to many of the available recorders: https://www.bhphotovideo.com/c/buy/Portable-Digital-Recorders/ci/14934/N/3992462091. I'd suggest reading reviews to see which matches your needs and get some advice from your rental company.
     
  6. KingKenny04

    KingKenny04 Registered

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    I may have access to rolling dynos. Would that be preferable? I would have thought the echo of being indoors would ruin any recordings?

    Also can you explain what you mean by keeping revs consistent off-throttle? I would think that's not possible, don't you need the throttle open to get a certain rev limit?

    Also can you clarify some of the terms I'm reading? I thought "loaded" meant the car was in gear, "unloaded" meaning in neutral. Does this mean something else?
     
  7. peterchen

    peterchen Registered

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    One thing to add what first came into my mind:
    If the car is rather loud, be sure the mic you use for external sound (near exhaust) is able to work with high db-levels, otherwise you have just clipping/distorted sound.

    Edit: I would forget the dyno-idea. Emery had the idea that using a dyno would "lock out" other noises, but the opposite is the case. A dyno makes loud noises that will ruin the recording and you can´t really filter it out as it overlaps with frequencies of the engine. Plus the room-noises you mentioned.

    On load means in gear and providing power to the wheels.
    Off load means in gear and with drag torque/compression.
    The idea is to "roll" the car downhill so you can hold the rpm needed for min. 10 seconds or so.
     
    Last edited: Mar 22, 2017
  8. Emery

    Emery Registered

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    Last edited: Mar 22, 2017
  9. peterchen

    peterchen Registered

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    Nice read. Thanks!
    Now that I thought it over, I think dyno could be a solution. As long as you stay in first gear, dyno is not reving much and so makes less noise.
    Is worth a try....
    The video you posted isn´t on a dyno. Car is just hooked up at the back.
     
  10. lordpantsington

    lordpantsington Registered

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    The dyno pictured in that Mustang vid is a hub mounted chassis dyno.
     
  11. racer11

    racer11 Registered

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    so what if a dyno and hills aren't an option? we cant just record the engine at a set RPM in neutral?
     
  12. peterchen

    peterchen Registered

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    OK, thanks. I thought already about it that there must be several dyno options that are working different as the ones I know of....
    Not really. As I wrote: you need the engine-break-situation somehow.
     
  13. Emery

    Emery Registered

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    Recording the engine in neutral won't have the same sound as a loaded engine. It will "work", but it will be lacking. Open up a good-sounding mod and listen to the difference between the offmid and onmid .wav files.
     
  14. racer11

    racer11 Registered

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    on stands and in gear? I just don't see a way to record the handful of cars I'm being allowed to play in without getting a shit ton of wind noise from hanging a mic out by the exhaust while we drive around. plus it's WAY easier to maintain the same idle speed by using an insert in the throttle cable/arm to hold an RPM that I wouldn't trust doing if the car was actually moving..
     
  15. peterchen

    peterchen Registered

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    Did you read the whole thread and what Emery wrote?
    Use a wind-absorber on mic and don´t drive fast!
    Driver should be able to hold rpm for 10 seconds or so, otherwise tell him to put out his lead-boots and take sneakers on!;)
     
  16. racer11

    racer11 Registered

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    I did read it but even in 1st gear a 333 Ferrari at 10,000 RPM is moving fast enough where you'll hear the bumps for the place we'll be at. It's about 85mph at that and the rears get light and thus pick up RPM. plus I don't know if those socks are good for that much wind
     
  17. Emery

    Emery Registered

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    Well... that's why the pros spend money instead of trying to do it for free.
     
  18. Emery

    Emery Registered

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    Judging by this recording, gearbox whine will be worse than the bumps. Not obvious whether the mic is in the cockpit or near the camera.

     
  19. racer11

    racer11 Registered

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    I don't think you understand how much money is actually being spent to pull out a 333 which would not have otherwise been running specifically for the purpose of building it into a mod but sure go ahead and keep thinking it's "free" ;) working on a lot more than just sounds that weekend

    so back to the questions: is this all I'd need to load the wheels? http://www.dynomitedynamometer.com/_selector/automotive/axle/2wd/eddy/044-100-1k_specifications.htm

    If not, do wind socks actually work for 80+mph? even on a dyno, gear whine is still a thing even in 1st gear so how do you separate the 2?
     
  20. Emery

    Emery Registered

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    Yes, dynos like those are the best for sound recording.

    Microphone selection (highly directional?) and placement are the first step to removing other sounds. Getting/setting sound levels is the second step. You might be able to muffle the gearbox with non-flammable insulation. If you have a contact mic on the gearbox, you might be able to subtract its waveform from the exhaust sample in post-processing, which is part of the reason I suggest a multitrack recorder, so you can keep the recordings in sync.

    Honestly, if you've never done a recording like this before and you're working with a high-end car on a time/money budget, practice with other vehicles first. If you've got a chunk of money you're throwing at the project, it might be wiser to hire a pro.
     

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