<html class="apple-mail-supports-explicit-dark-mode"><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">Adding to Stephen’s excellent message: Surface (wall, floor, ceiling) mass and vibration isolation, along with air gaps all matter for noise originating outside a space.<div>Not sure how much that helps here!<div><div dir="ltr"><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature">Bruce</div></div><div dir="ltr"><br><blockquote type="cite">On Mar 27, 2026, at 15:25, Jon Ares via Stagecraft <stagecraft@theatrical.net> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><div dir="ltr">I'm finding this thread interesting as well. There is a low frequency in my bedroom as well some mornings - I only hear it when my head is on the pillow, or slightly above it. I can't hear it if I sit up, or leave the room. I think it's maybe a neighbor's heat pump. It's not my heat pump, or fridge, and I don't have a furnace.... I've stepped outside when I've been hearing/feeling it, and I can hear the soft whoosh of the neighbor's heat pump, but no low frequencies. I've made sure the bed frame doesn't touch the wall, but I still hear it. A mystery. <div><br></div><div> - Jon</div></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Fri, Mar 27, 2026 at 12:07 PM Don Taco via Stagecraft <<a href="mailto:stagecraft@theatrical.net">stagecraft@theatrical.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><div style="font-family:arial,helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><div><br></div><div> This got me intrigued, and I quickly found out that there are all sorts of youtubes of generated tones. I couldn't hear the 8 kHz tone at all at first, but after trying a few lower and higher tones, I found I could hear it if I cranked the speakers up high enough. And I can certainly see that it would be annoying and how motivated you'd be to discover the source. Happy hunting!</div><div><br></div><hr id="m_8432386474847879707zwchr"><div><b>From: </b>"Tim Catlett via Stagecraft" <<a href="mailto:stagecraft@theatrical.net" target="_blank">stagecraft@theatrical.net</a>><br><b>To: </b>"Stagecraft Mailing List" <<a href="mailto:stagecraft@theatrical.net" target="_blank">stagecraft@theatrical.net</a>><br><b>Cc: </b>"Tim Catlett" <<a href="mailto:tmcatlett@gmail.com" target="_blank">tmcatlett@gmail.com</a>><br><b>Sent: </b>Friday, March 27, 2026 11:40:37 AM<br><b>Subject: </b>Re: [SML] 125Hz room resonance<br></div><div><br></div><div><div dir="ltr"><div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small">Thank you Steven.</div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small">I really appreciate the information and the ideas.</div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small">Regarding the 8KHz sound, that is only the "perceived" tone, measured against a tone generator and subjectively identifying the correct, or close enough, tone that is being "heard."</div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small">The tinnitus, and many other physiological effects, can indeed be caused by low frequency tones, which is what we experienced multiple times at protests in Minneapolis.</div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small">This is the first time something like that has ever happened in my bedroom.</div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small">I know that was the cause because the tinnitus would reduce when I walked away from the room and went outside. It would also disappear after a full day at work, only to reappear shortly after I returned home.</div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small">I'm going to try some different strategies and see what happens.</div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small">Again, thank you for the info and I'll try to report back with any further details.</div><br clear="all"></div><div><div dir="ltr" class="gmail_signature"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div style="font-size:12.8px"><div style="font-size:12.8px"><div style="font-size:12.8px"><div style="font-size:12.8px"><div style="font-size:12.8px"><b>Tim Catlett</b></div><div style="font-size:12.8px"><b>(414) 975-4424</b></div><div style="font-size:12.8px"><div><div style="font-size:12.8px"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div style="font-size:12.8px"><div><a href="mailto:tmcatlett@gmail.com" style="color:rgb(17,85,204)" rel="nofollow noopener noreferrer" target="_blank">tmcatlett@gmail.com</a><br></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Mar 26, 2026 at 12:23 AM Stephen Lee via Stagecraft <<a href="mailto:stagecraft@theatrical.net" rel="nofollow noopener noreferrer" target="_blank">stagecraft@theatrical.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="font-size:10pt;font-family:verdana,geneva,sans-serif">
<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>
<p><br></p>
<p><br></p>
<p id="m_8432386474847879707m_-5217123220447524882reply-intro">On 2026-03-25 1:54 pm, Tim Catlett via Stagecraft wrote:</p>
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<div style="font-family:verdana,sans-serif;font-size:small">Hey all,</div>
<div style="font-family:verdana,sans-serif;font-size:small"> </div>
<div 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>
<div style="font-family:verdana,sans-serif;font-size:small"> </div>
<div 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>
<div style="font-family:verdana,sans-serif;font-size:small"> </div>
<div 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>
<div style="font-family:verdana,sans-serif;font-size:small"> </div>
<div style="font-family:verdana,sans-serif;font-size:small">Any advice?</div>
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