AFMG Network Forum

rumoon · Member

I'm modelling a small room (8m x 12m approx) with two large cabinets towards the centre and a single wall-mounted loudspeaker.

Where there is a "shadow" from the loudspeaker's output I am getting zero direct SPL and (more importantly) zero STI using standard mapping.

Total SPL seems reasonable, but it's the zero STI which makes no sense. Varying split time has no effect.

Any ideas?

rumoon · Member

...but if I un-tick "Map with Shadows" it looks OK*. I'm clearly not understanding this option, so any information would be gratefully received!

*for some value of "OK"; it actually looks like it is ignoring the obstructions but in a small room this seems more accurate.

AFMG Pedro Lima · Forum Moderator

Dear rumoon,

Please use the Search resource to look for existing threads before creating a new topic. Wink

Here you can find more info on Shadow Casting:
http://afmg-network.com/viewtopic.php?t=1488&highlight=shadow+cast
http://afmg-network.com/viewtopic.php?t=1341&highlight=shadow+cast
http://afmg-network.com/viewtopic.php?t=1314&highlight=shadow+cast

Kind Regards,

rumoon · Member

Thanks very much for the reply. I have actually seen those replies. So are you saying that you think an STI of 0 in a small room with one loudspeaker would be experienced in real life? I don't think it would, so I am wondering where I am going wrong.

Jim Mobley · Member

Hi Rumoon,

STI is basically signal to noise ratio, with the direct SPL being the signal. If the direct sound is 0 dB-SPL due to shadowing, then you're going to get an STI value of 0. In the real world, you have reflections and diffraction around the solid objects, but the simplified calculation in Standard Mapping doesn't consider those factors.

You can consider reflections by doing a Ray Tracing or AURA calculation, diffraction will need to wait until the next version of EASE.

What is your goal here? Just experimenting to understand EASE, or do you really need to predict the loss of intelligibility caused by these two cabinets?

rumoon · Member

Hi Jim thanks for the reply, that makes sense. I'm just doing some predictions for a pa system report, the cabinets are really only there so the customer can recognise their equipment room!

In reality I doubt they would have much of an effect so it may be simpler to remove them.

My main concern was that I was doing something stupid!

Ron Sauro · Member

If you need to have the cabinet in the room for orientation you might try to draw it with edges instead if you do not think the shadowing is not that important.

rumoon · Member

Thanks for the info. At this stage I have limited the report to Total SPL and will not be sharing any STI or Direct SPL plots, so it's not an issue.

I am looking forward to the next EASE version though - does anyone know when this is planned?