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<p>A couple of thoughts: </p>
<p>- I'm not sure how a resonance in your room (especially at such a low frequency) would give you Tinnitus at 8kHz. Are you sure the 8k isn't being generated by a CRT TV, electronic device, or switch-mode power supply (which are in just about everything these days)? You can use your RTA (or even a free RTA app on your phone) to listen close to devices and find the source of errant noise. </p>
<p>- There are acoustical room mode calculators online that can give you the frequency peaks for a room of any size. Just enter the dimensions and it will calculate the resonances. Studio designers use these all the time to play with different room sizes before the walls go up. </p>
<p>- I'm not surprised that a blanket had little effect on the low-frequency issues in the room. Low frequencies have long wavelengths and tend to be unaffected by materials that are thin.</p>
<p>A good rule of thumb to use when designing wall treatment and absorber panels is the 1/4 wavelength principle. The material will start to lose effectiveness at wavelengths which are longer than the thickness of the material x 4. As an example, a 1kHz frequency has a wavelength of around a foot. If you cover a wall with fiberglass, you'd want it to be at least 3 inches thick to fully absorb frequencies from 1kHz and above.</p>
<p>A 100Hz frequency has a wavelength of about 10 feet, so things start to get challenging. There are a couple of things you can do to cheat the system, though. One is that the most effective slice of absorber material is the section right at the face, so if you need 2.5 feet of thickness, you can get most of the same results by getting a panel that's just a few inches thick and spacing it away from the wall by 2.5 feet. Another cheat is that small rooms (relative to the size of the wavelength) can often get away with far less material if strategically placed. The corners of a room are a good way to get distance away from a wall with less sacrifice of the room's useable space. Try hanging the same blanket across the corner of your room and see if that makes any difference. </p>
<p>Stephen Lee</p>
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<p id="reply-intro">On 2026-03-25 1:54 pm, Tim Catlett via Stagecraft wrote:</p>
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<div class="v1gmail_default" style="font-family: verdana,sans-serif; font-size: small;">Hey all,</div>
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<div class="v1gmail_default" style="font-family: verdana,sans-serif; font-size: small;">I've just encountered a problem that I think this group is well equipped to assist me with. While not directly stagecraft-related, stagecraft (and audio) knowledge is applicable. I deeply appreciate any advice in advance.</div>
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<div class="v1gmail_default" style="font-family: verdana,sans-serif; font-size: small;">My bedroom seems to have developed a 125Hz resonance (along with one more significant one at about 33Hz), which seems to have prompted my brain to give me "observational(?)" tinnitus, which is consistent tone with a perceived value of about 8KHz. It's very annoying.</div>
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<div class="v1gmail_default" style="font-family: verdana,sans-serif; font-size: small;">I tracked the tone around the room with an RTA and was able to identify a "hotspot", but it seems that even hanging a heavy soft-surface (woven wool blanket) has not dampened the problem. I'll also try putting foam behind the television when I get home today.</div>
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<div class="v1gmail_default" style="font-family: verdana,sans-serif; font-size: small;">Any advice?</div>
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