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<blockquote data-quote="Art Welter" data-source="post: 140620" data-attributes="member: 52">Re: dBA - dBC for EDM in an old castleCharlie,It only takes seconds for low frequency content to cause structural damage if the resonant frequency of the &quot;delicate ceilings&quot; is excited, so a 90dBA limit, as an average over 60 minutes, tells nothing about the SPL energy delivered to the structure down low, as dBA is -40 dB at 20 Hz. If an electronic drone 20 Hz tone read 90 dBA, it would actually be 120 dB SPL, which could potentially cause structural damage. I know from experience that short impulses of kick drum of around 120 dB definitely can cause plaster to crack and fall off ceilings.DBC also rolls off below 100 Hz, it is about -6 dB at 20 Hz. You really need a dB meter flat to 20 Hz for what you want to measure.I have found in my home studio that around 100 dB SPL somewhere between 15-20 Hz can make the 5/8&quot; drywall (sheet rock panels) &quot;flap&quot;, if that level was continued for more than a few seconds, screws would be pulled out and joints would crack.To actually determine what frequencies excite the various portions of the castle ceiling, and what level at what frequencies and duration will cause damage would require destructive testing.Art</blockquote>

[QUOTE="Art Welter, post: 140620, member: 52"] Re: dBA - dBC for EDM in an old castle Charlie, It only takes seconds for low frequency content to cause structural damage if the resonant frequency of the "delicate ceilings" is excited, so a 90dBA limit, as an average over 60 minutes, tells nothing about the SPL energy delivered to the structure down low, as dBA is -40 dB at 20 Hz. If an electronic drone 20 Hz tone read 90 dBA, it would actually be 120 dB SPL, which could potentially cause structural damage. I know from experience that short impulses of kick drum of around 120 dB definitely can cause plaster to crack and fall off ceilings. DBC also rolls off below 100 Hz, it is about -6 dB at 20 Hz. You really need a dB meter flat to 20 Hz for what you want to measure. I have found in my home studio that around 100 dB SPL somewhere between 15-20 Hz can make the 5/8" drywall (sheet rock panels) "flap", if that level was continued for more than a few seconds, screws would be pulled out and joints would crack. To actually determine what frequencies excite the various portions of the castle ceiling, and what level at what frequencies and duration will cause damage would require destructive testing. Art [/QUOTE]

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