recording double bass outside.

This depends a great deal on the pickup pattern of the microphone that you are using, its placement relative to the speaker, and the location of the speaker and mic inside the room. If it is a cardoid or unidirectional microphone, then the standing waves inside will not have much effect on the recorded signal. If the speaker and mic happen to be placed at a spot where standing waves augment the direct sound, then the bass will be louder and have less character than if the speaker and mic are at a spot where the standing waves cancel out the direct sound.

Question: Am I dealing mainly with the characterists of the bass rather than with the office acoustics? Yes, I know that bird calls and wind are present in the out-of-doors recording, but the lack of appreciable decrease in dB after hitting the string was very pronounced.

Do you mean that the signal decreases more or less outside?

I may be misunderstanding your post, but the purpose of a bass trap is to even out the frequency response in a room. In theory, by using bass traps you can simulate being in a larger space and reduce some of the destructive interactions between primary and reflected sound waves at certain frequencies. This should make music sound better in the room and cure some instances where certain notes (especially bass notes) sound quieter than they really are.

the lack of trapping in the office resulted in a more prolonged decrease in the magnitude of the wav dB

I really don't know what you are talking about here. Are you playing some notes, then stopping, and noting how long it takes for your mic to cease picking up any sound energy? If so, that is more a function of natural reverberation and/or how much noise you make after playing your last note.

And a wild thought. Since I live up here in NYS in farm country, how would a bunch of bales of hay work as traps? Can't beat $2 bucks per bale (they weigh about 80lbs)

You can certainly try it, but I have a feeling that purpose built bass traps would probably give better results and take up a lot less space.

ORIGINAL: Thomas Campitelli

I may be misunderstanding your post, but the purpose of a bass trap is to even out the frequency response in a room. In theory, by using bass traps you can simulate being in a larger space and reduce some of the destructive interactions between primary and reflected sound waves at certain frequencies. This should make music sound better in the room and cure some instances where certain notes (especially bass notes) sound quieter than they really are.

the lack of trapping in the office resulted in a more prolonged decrease in the magnitude of the wav dB

I really don't know what you are talking about here. Are you playing some notes, then stopping, and noting how long it takes for your mic to cease picking up any sound energy? If so, that is more a function of natural reverberation and/or how much noise you make after playing your last note.

And a wild thought. Since I live up here in NYS in farm country, how would a bunch of bales of hay work as traps? Can't beat $2 bucks per bale (they weigh about 80lbs)

You can certainly try it, but I have a feeling that purpose built bass traps would probably give better results and take up a lot less space.

The effects of "not bass trapped" rooms are very hard to predict and may lead to any number of circumstances, from "boomy, muddy" rooms, to "weak, un-bassy rooms" to overly "ringy" rooms, or whatever. Low-frequency soundwaves are very hard to manage and are best dealt with in smallish spaces by simply being totally eliminated. They have enough sound energy that there is generally no need to reinforce them. Even if you can precisely calculate the resonances and room modes, there is virtually zero benefit to targeting your bass management to particular frequencies.

The fact is, unless you want to spend many tens of thousands of dollars on an acoustical contractor, the best bet is simply to use broadband low-frequency apsorption. This could mean purpose-built broadband helmholtz resonators, or some realtraps in corners, or some homemade rockwool panels, or or some stacks of pink fiberglass, or bales of hay, or dirty laundry, or old mattresses for that matter. Moreover, an old mattress in the corner will easily rival an acoustician's best efforts when it comes to bass management.

Room acoustics are often given either far too much or far too little attention by home recordists. The fact is, every single Motown recording (before Motown moved to LA) was made in a small rectangular basement. All of John Hammond's recordings of the
Benny Goodman orchestra (including all the Charlie Christian records) were made in a rectangular, low-ceilinged room with one mic. Room treatment in these classic "studios" basically consisted of some pegboard on the walls with fiberglass insulation behind, and these are some of the great recordings of all time.

Ethan Winer ( a frequent poster on these forums) runs an excellent company that sells great broadband bass traps (called "realtraps"). His website also provides a lot of detailed and very honest information about room treatment. His company produces products that are very easy-to-install, cosmetically tolerable, relatively inexpensive solutions. But the fact is, stacks of baled hay or pink fiberglass rolls or mattresses or piles of dirty laundry essentially work just as well for broadband bass absorption.

Cheers.

Consider this: since "Q" refers to the ability of a device, be it electronic, or acoustic, to store energy, part of the diminuition effect you are observing may be due to the higher Q of the air confined in the room, as opposed to the lower Q of the open air outside. So, as the insrument imparts it's energy upon the room, this energy is stored therein for a longer time period, thus increasing the probability that the room will impart a larger and larger portion of the energy it has received from the instrument, back to the instrument.

Electric Guitar players call this sustain, it is actually frequency selective (following room nodes) feedback.