very odd feeling at a concert

I had an interesting experience last weekend and want to know how the mechanics of my pacer handles such an event.
Here goes: I went to hear/see the Blue Man Group on Saturday. They played in a Civic Theater which seats about 1200 and is normally used for plays, musicals and ballet. I was seated in the 20th from the stage, dead center. There were many large to huge speakers rigged around the stage. The act opens to a very low bass sound that swelled to a roaring rumble that vibrated my chair, me, my chest, my hair, etc and I began to feel bad. I felt like my pacer was in a different rhythm. Once the loud sound subsided, I was fine again. This was repeated many times during the course of the concert/show. If I sat forward, the effect was not as recognizable or the feeling so bad. So here is my question. When one is in a seriously loud, vibrating environment, will a pacer switch to a safe mode until the offending vibration dissipates?

And if it does switch to a safe mode sort of setting, will that show in an interrogation?

Regards,
ksig

8 Comments

safe mode

by Tracey_E - 2014-03-29 05:03:40

If it switched modes, it will show up when it's interrogated. The speakers have large magnets which can affect us if we get too close. If you are physically vibrating and you pace with rate response, it can think you are exercising and raise your rate for you. It could also be something inner ear, possible eye since they use a lot of strobe lights, thing like that can affect us but not be cardiac.

I felt what you are describing once during a Kenny Chesney concert on an especially loud song at the end of the encore. I've been to dozens of concerts in the years since I got the pm, including half a dozen KC, with seats everywhere from the very front to practically in the parking lot, but it only happened that once. There was nothing in my pm report that time. I've been to BMG, also, we were close but not close enough to be offered ponchos.

Hope it didn't ruin the show for you! BMG is a lot of fun. As long as you feel ok now, I wouldn't worry about it.

Me too

by Alma Annie - 2014-03-29 09:03:19

This happened to me at an open air funeral when I was standing in front of one speaker. I had no idea at the time that speakers contain magnets. I felt so peculiar that I had to sit down, as I thought I was going to pass out. Away from the speaker it took about 15 minutes to get back to normal, then I was fine. It was only later that I found out what caused the problem.
Alma Annie.

Concerts

by Marie12 - 2014-03-29 09:03:40

I had this happen to me also at a concert. At the time, I didn't even know large speakers had magnets and I was in the front row less than six feet away. Nothing showed up during the interrogation of my ICD/Pacemaker so I don't think it is anything truly to worry about.

Tracey: I'm Gonna.....

by donr - 2014-03-29 11:03:17

.....disagree w/ you on this one.

There is not a permanent magnet that humans could carry strong enough to affect the PM in the 20th row. Even the superconductor magnet in an MRI will not get you at that range.

This one is pure & simple vibration affecting the RR device in the PM. Medtronic uses an accelerometer to sense motion of the upper body. That is nothing more than a very small mass of metal attached to a spring & a sensor. Just like the devices in the guidance systems in missiles & navigation systems in aircraft. If the body moves at all, whether by its own muscle power or if it vibrates as Ksig describes, that accelerometer is going to move & the sensor will generate a signal that the computer thinks is exercise or motion of the body.

In this case, however, somewhere in the frequency of that heavy sound was a vibrational frequency that matched the mechanical phenomena called its "Natural Frequency." At that point the little mass has the greatest movement & Will really generate a wicked signal. Unfortunately, that signal will most likely be changing much faster then the body ever moves & the PM gets confused & drives the RR function nutso.

My guess, therefore is that she was feeling a truly confused RR device trying to affect the HR.

Now the way she described the feeling, she felt it in her chest. Also buried in that bass was a frequency that matched the Natural Frequency of her body cavity - most likely the lung cavity. For sounds, it is called the "Resonant Frequency." Blow across the open mouth of a Coke bottle (If you can find one) or a Budweiser bottle. The sound you hear is its resonant frequency. Same thing w/ the chest cavity. You feel it vibrate at its Resonant Frequency.

Donr

Thanks

by ksig - 2014-03-30 04:03:48

Donr your explanation makes a lot of sense to me. I knew this had to be a sound engineering problem and not a problem with my heart. Your explanation was easy to follow and I appreciate your time to write the explanation.

TraceyE: I knew I was too far away from the speakers for the magnet effect to take place. I knew it was vibrating sound that was causing my discomfort. Since I am 100%pacer dependent, I am always fascinated by things that effect my pacer/heart.

I appreciate the quick responses from this community. Best to all of you.
ksig

A Small Experiment for you to try...

by donr - 2014-03-30 06:03:45

.....Ksig: Try this. I did it today & it worked.

If you'd like to learn the resonant frequency of your chest cavity, fill your lungs w/ air, close your mouth & start "Humming " at the lowest frequency that you can. Vary it up & down slowly. If your vocal cords are capable of going low enough, the instant you hit that frequency you will feel your entire chest start vibrating & the sound will instantly become louder. I don't think you can activate your PM's accelerometer this way. I assume you are a woman, so there is a fair chance that your vocal cords will not be able to go low enough. But any man out there short of being an Irish Tenor should be able to do it.

Sitting in the audience so close to the speakers, they generated a LOT of sound energy & when it hit the resonant frequency of your chest, it was significantly amplified.

Anyone out there old enough to remember Bowser, the bass member of the TV rock group in the US called Sha Na Na? He could probably generate enough voice energy to activate the accelerometer.

I vividly recall a Humongous church organ that was capable of putting out enough energy at the correct frequency to make the interior volume of the building resonate. The organist always hit that note after the sermon to wake everyone up. It was practically inaudible to the ears, because it was too low, but you sure could feel it in the chest & feel the air in the building vibrate.

For the rtruly curious, if you want to see what a small amount of energy coupled into a steel structure can do, Google on "Tacoma Narrows Bridge Failure." Back about 1940, the wind hit just the right velocity perpendicular to the bridge & it started vibrating & destroyed itself. There should be a video of that disaster on some web site.

Every engineer in the world knows about that disaster.

Don

no reverberation can be duplicated ;(

by ksig - 2014-03-30 08:03:16

Hi, Donr
I tried the experiment to no avail. My tone is too high as I am a female as you guessed. But I had fun trying! Funny you talked about the ShaNaNa group. In the 70s I saw them in person and have a faint remembrance of Bowser's low voice.

All in all, I had a very interesting experience and wanted to know the mechanics of it all. I appreciate your time and interest.
ksig

And to put a name to it

by KAG - 2014-03-31 12:03:41

it's called Acoustical vibration. Don gave a very good explanation as usual. Same effect happens when you're at a stoplight and a car near you has mega speakers blasting out the bass. You can feel the vibrations.

No wonder it can make you loose your hearing.

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