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[JamesJudson]

Hey there, I know that bad acoustics can reduce the overall systems intelligebility and in order to understand speech in such acoustically challenging environments sound designer has to make sure that the audience are in coverage of the speakers to increase direct to reverberation ratio. I was wondering if such bad acoustics can contribute to systems gain before feedback and how do they effect my GBF. I need help please. Can someone explain or leave a link to potential article that explains this?

[Keith Broughton]

I'm sure someone here can post a study on this but my initial take is this...
In an bad acoustic environment, where intelligibility is low, most people with want to increase the volume in a misguided notion that louder is clearer.
This will challenge your GBF threshold!
I would also conjecture that if the room had many reflective surfaces, the reflected sound could negatively affect a microphone's directional capabilities to reject off axis sound sources.

[JamesJudson]

I'm sure someone here can post a study on this but my initial take is this...
In an bad acoustic environment, where intelligibility is low, most people with want to increase the volume in a misguided notion that louder is clearer.
This will challenge your GBF threshold!
I would also conjecture that if the room had many reflective surfaces, the reflected sound could negatively affect a microphone's directional capabilities to reject off axis sound sources.

can you be more specific about "how room reflections can negatively affect mic's directional capabilities"

[John Roberts {JR}]

Strong room resonances can affect GBF.

Feedback is affected by the total path frequency response.

JR

[Jordan Wolf]

In highly reflective and/or reverberant rooms, it is a fine balance of compromise. If you can figure out the critical & limiting distances, you’ll have some idea of how your loudspeakers will best be deployed.

After that, I’d focus on loudspeaker pattern control (put the sound where the listeners are AND not where they aren’t), proper mic technique and mic selection, and seeing what SPL you need for your services.

Having coverage zones that are time-aligned and EQ’d to reinforce the main “image” of the PA system go a long way to increasing overall intelligibility, in my experience.

All of the above will play a role in how much GBF you can achieve.

[Chris Grimshaw]

Simple thought experiment:

Situation 1 - Mic and speaker in an anechoic chamber. The speaker and microphone are both high-quality and keep their directional patterns well. GBF is basically infinite.

Situation 2 - Take S1, and add two "acoustic mirrors" (a device I just made up, but you already know what it does). Position one in front of the speaker, and one in front of the microphone, arranged such that the speaker's output reflects into the microphone's sensitive side. GBF is now very low.


All real-world situations are somewhere along that scale. Good luck.

Chris

[John Roberts {JR}]

Simple thought experiment:

Situation 1 - Mic and speaker in an anechoic chamber. The speaker and microphone are both high-quality and keep their directional patterns well. GBF is basically infinite.

Um no unless you have infinite pattern off axis attenuation, and both are positioned off axis.

Situation 2 - Take S1, and add two "acoustic mirrors" (a device I just made up, but you already know what it does). Position one in front of the speaker, and one in front of the microphone, arranged such that the speaker's output reflects into the microphone's sensitive side. GBF is now very low.

real world sitchs are complex enough....

Dominant feedback modes are direct path. Near field reflections can alter path response and feedback susceptibility.

JR

All real-world situations are somewhere along that scale. Good luck.

Chris

[JamesJudson]

Strong room resonances can affect GBF.

Feedback is affected by the total path frequency response.

JR

hey where can I learn about this 'dominant modes and path response' and stuff, are there any articles on internet or books?

[John Roberts {JR}]

Listen to the posters here....

JR

[Dave Pluke]

hey where can I learn about this 'dominant modes and path response' and stuff, are there any articles on internet or books?

Google "acoustics textbook" and peruse the results.

Dave

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