Best practices for auditory stimuli in fMRI

I am curious to hear about what people use to present auditory stimuli in fMRI experiments.

I am currently using a sensimetrics system in a 3T prisma, but I am not happy with the level of hearing protection - this uses disposable foam earplugs.

I am now looking into this ultraslim active noise cancelling system https://www.optoacoustics.com/sites/default/files/documents/optoactive_brochure_2020-lite.pdf

Any feedback about best practices or experience with these systems would be really appreciated.

Sensimetrics seems to be the best option available, as it has a good/flat response profile up to 10 kHz and a small housing profile (particularly on the newer 7T+ compatible Sensimetrics S15 system).

Typically, foam ear plugs are actually quite effective at sound attenuation. However, as with any foam ear plug/tip, sound attenuation with Sensimetrics ear tips is very dependent on ear tip placement within the ear canal.

See the Technical note on attenuation PDF on their documentation site: appropriate placement gives you ~30 dB attenuation (essentially as good as acoustic attenuation can be), but bad placement provides only 10 dB attenuation.

Before buying a new system, I’d recommend getting familiar with optimal practice for foam earplug insertion. This is something every participant needs to be carefully walked through, since many people assume they know how ear plugs work but insert them ineffectively.

Finally, it may be necessary to get multiple sizes of ear tips, as ear canal shape/size varies quite a bit. The Sensimetrics shop has a few different options.

Good luck!

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This is very useful thank you!
I have not tried to carefully optimize placement or the size of the earplug, so there may be gains to be had there indeed. I will definitely try that.

We’ve also successfully built custom earmuffs for double protection on top of the sensimetrics (with the 7T compatible system you are referring to). It is helping and comfortable for some subjects, but too tight for others (on a 64 channels Siemens prisma coil).

Thanks again for the feedback and the pointers.

We also use Sensimetrics (S14), plus foam pads to prevent head motion and added sound attenuation.
So far, we’re quite happy with it.
EDIT: Prisma, with both 32- and 64-channel coils

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That’s great, if you can afford it. How much does the system cost?

We use the sensimetrics, but also have the subject wear headphones on top of that. This provide pretty good attenuation.

Best,

Mark

@pvelasco, thanks a lot for the feebdack!

@mwagshul re the optoactive system, I don’t really want to bypass their “request a quote” page :slight_smile: But it’s fair to say it’s substantially more expensive than sensimetrics.

If you don’t mind providing a bit more details, what kind of MRI/coil do you use? and what headphones? thanks!

We are using a Philips Elition 3T. The headphones are from Resonance Technologies. We have also used the Philips headphone, but you have to remove the yellow insert which normally presses against the ear as this will push the Sensimetric earbud in too much and be very uncomfortable for the patient.

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pinging @PeerHerholz :upside_down_face: who might be of help here?

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I’ve been using the Sensimetrics S15 system and get decent attenuation. However, sometimes jaw or head movements can shift the earplugs. It would be nice to have a way to easily secure them. I’ve used acoustic putty to mold individual ear inserts and inserted the s15 into that. This method works well if you have participants returning multiple times, but take ~30 minutes to make and you have to be very precise when drilling the hole for the S14/S15 tip. Headphones are a great solution if you can get them inside the headcoil, but there usually isn’t enough space - we may have large-headed participants. For psychoacoustic studies, we’ve relied on clustered acquisition sequences with good success. Looking forward to seeing other solutions folks have found. [quote=“pbellec, post:1, topic:18316, full:true”]
I am curious to hear about what people use to present auditory stimuli in fMRI experiments.

I am currently using a sensimetrics system in a 3T prisma, but I am not happy with the level of hearing protection - this uses disposable foam earplugs.

I am now looking into this ultraslim active noise cancelling system https://www.optoacoustics.com/sites/default/files/documents/optoactive_brochure_2020-lite.pdf

Any feedback about best practices or experience with these systems would be really appreciated.
[/quote]

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Thanks for the feedback Axelander, very much appreciated. I’ve made a pair of custom mold eaplugs for myself with the same trick you describe. I’ve drilled the hole with a drill bit I rotated gently by hand. It is super comfortable, but I don’t think it provides more protection (maybe even a bit less). This is a n=1 hack project though :hear_with_hearing_aid:

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