Hi all,

Currently working on a project where the use of "off screen" background sounds (ie streets, car passbys, crowds etc)in interior locations is very important. Any interesting tips on effectively making recorded sounds appear more like they're coming through a wall/obstruction?

Obviously been playing with EQ, volume and reverb, as well as editing the sounds so nothing too transient sticks through, but was wondering people's fave tips were on this?

Any particular EQ shapes, reverb types/settings that are particular "go to's" would be cool to hear!

Worldizing isn't an option for me on this though, but I guess that'd be one future option! Cheers

8 Answers 8


Proper stereo image is also important. One of the reasons many exterior BGs don't seem to work at first for interior locations is that they're too wide. If you pull them in quite a bit (maybe even mono all the way for some) it helps a lot. Same with distant car passes and the like.


Offstage exterior "bleedthru" sounds I believe are one of the great challenges of backgrounds - up there with wind, ocean/beach textures, and rain. In terms of how to paint it sonically so it pops, but doesn't draw unwanted attention to itself, while also not sounded like a muddy mess of frequencies with a lack of clear intent.

The hallmark to doing this kind of "bleedthru" work, in my opinion, begins with properly establishing the correct type of roomtone for the space. Roomtone may seem like one of those "ah, roomtone, whatever" type sounds - something you just quickly slap in. I think it couldn't be further from the truth. Often in a scene I spend time determining what the space should sound like even before painting in 'textures of life'. No amount of processing or manipulating of bleedthru backgrounds can compensate for having established an inappropriate roomtone. How big is the space? Is it reverberant (like a warehouse or rotunda, or dampened like a bedroom)? What sort of airflow does it have (dead air with a slight clean hiss versus an HVAC vent system, wherein you might hear a light hum or lower frequency content and less of the "quiet' hiss)? How techy of a room is it? Could there be fluorescent buzzes or compressors or fans droning? Whenever I'm establishing a space, even a subjective space like a sci fi operations control room or interrogation room or a generic realistic space, these are the questions I always ask myself before laying in anything - questions I ask while audition source material. Searching, auditioning until I find the textures which hit my ear right. Sometimes it only takes 2 tracks to achieve the sound I want for a roomtone, sometimes it can take 5-6 (believe it or not a 'dead quiet' European opera house I recently cut, pre-performance, commanded about 7 particular roomtone layers to achieve just the right kinds of pleasing, crisp, spacious, cavernous, and dead quiet sound I wanted). But I feel that this is a very important first step.

Once you've determined this, the bleedthru stuff should play very low - often so it's just barely tickling the ear over the roomtone (which is why the proper roomtone is so important!) The roomtone serves almost as your "calibration", so if you have incorrect roomtone, which results in either hearing your bleedthru sounds too crisply/naked, or having to boost them to sound too present in order to cut through the roomtone, then all you're doing is working against yourself.

98% of the time I use exterior-recorded sounds for bleedthru elements - occasionally applying a touch of reverb if needed, but often I leave this up top the stage to handle. I almost NEVER do any EQ (except for notch filtering a highly-offending noise band or doing a roll off, such as unnecessary low end rumble on a bird track) Seeking exterior sounds which have a natural distance and reverb can help, but I even use clean, nearby sounds without much trouble and don't find it bothersome in selling a bleedthru. It comes down to developing a sensibility for what "feels" right in terms of what source material you choose, but also the balance of your bleedthru sounds against your roomtone, the latter of which needs to be appropriate from the start. Whenever I strike this balance, what I hear, even clean ext elements, sounds natural to me and always have.

The stage will usually add the worldizing factor of where the elements get panned within the sound field and what type of a general reverb the BGz will be run through. But I have experienced times where no reverb treatments are used and you know what, the clean sounds,, just tickling the ear over the roomtone, still sound naturally to me and I buy what I'm hearing.

So these may be some things to consider, as well as not thinking too hard over this. BGz are exaggerated for a reason in film/TV, they don't sound right when played as reality would have it - reality is very boring-sounding.

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    -1 for SSD that I can't add more than +1 votes to a post. Nicely said, man. Jun 16, 2013 at 1:33

Just like when we hear dialogue through a phone, you aren't trying to document the actual process (although that may be handy as a reference) - you are trying to evoke the feeling and effect of elements outside the room, in the context of what else is playing in the soundtrack.

I'm not hassling the OP but its something worth considering: a while back a local young sound editor kept asking me to give him suburban ambiences for a project he was working on - interior and exterior. I would ask him: where do you live? "Suburbia" And you have a mic and recorder right? "Um, yeah" So, what exactly is stopping you from recording them yourself? "Um...

The only other things you need are effort and time. Do a lot of recording, in different places. And don't forget to use your ears eg record an interior ambience for half an hour, then half open a window, record another half hour, fully open the window record another half hour. Repeat this at different times of the day, and days of the week. Repeat it in every house or building you can access. And remember recording quiet ambiences, it is often better if you aren't there (breathing/rustling etc) So take a good book, set the mics up, hit record and go into another room for half an hour.

My point with the window is it allows you to go from hermetically sealed room, to practically an EXT perspective depending on where you place the mic...

And as @Stavrosound said, it will be more about the choices you make, as to what elements you use.


Lowpass filters usually do the trick. But if you're willing to go the extra mile (and if you have the equipment), you can record some stuff from inside and then compare the spectral analyses.

  • Yup, low-pass filter or a high shelf. Nothing too fancy required, although worldizing ought to be more like "the real deal". Jun 11, 2013 at 18:55

Altiverb "Next Door" impulse responses are great for this sort of thing.

Of course, nothing beats well recorded interior BGs.

  • That seems to be an area where I'm short of good indoor recorded BGs! Know of any good samples?
    – Andy Lewis
    Jun 13, 2013 at 18:24

@Stavrosound Very interesting answer! Thanks for sharing your workflow.

I'm curious about how you make use of stereo/mono sounds to build up the room tones and the "bleedthru" backgrounds. Are they mostly mono or stereo?

Cheers, Elena

  • Often a combo of the two - it particularly depends upon where I intend the sound will be placed (if it's going anywhere in LR or LsRs and I want it to have a wide spread, I go with stereo) and/or if there's a great natural reverb aspect. Mono is usually for location-specific sounds. It also depends on whether the source element is mono or stereo as well. No real hard and fast rules. Jun 13, 2013 at 16:34

Does making your own impulse response (at home) where you have the mic one room and the speaker in another (or even outside) count as worldizing?


Start by summing the source file to mono, then use EQ create a curve like an extreme S curve. Most of the low frequencies are transmitted through walls and windows with only limited colouration, whereas the highest frequencies are completely absorbed, this obviously varies according to material. I use Serato's Rane series Graphic EQ and end up stacking them to achieve sufficient cuts. Once I have done this the output can then be worldized like any other sound source.

  • Interesting -- Is there any particular reason why you use a graphic EQ for this?
    – Alex
    Jun 14, 2013 at 8:35
  • I need to make more precise changes across multiple frequencies, than 7 band allows. When you are simulating rooms you have to pay attention to the harmonics as well as the fundamental frequencies, so basically I find it easier with a 31 band.
    – user80
    Jun 14, 2013 at 10:48

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