You’re using high quality microphones in an acoustically treated boardroom, so in theory you should have the best conference sound available. So why are you still not able to hear the person on the far end of a video conference call clearly? It may be due to the placement of your ceiling loudspeakers.
Video conferencing has become a critical business tool for connecting you with your colleges and clients across the globe. Collaboration and meeting productivity is only achieved when each member of the meeting can be heard and can hear everyone consistently clearly. Proper loudspeaker selection and placement has a great affect on this experience.
Ceiling speakers in boardrooms are often found dotted along the ceiling sporadically, living in spaces that are not already occupied by HVAC, lighting and fire alarm equipment. There may only be a pair of speakers installed in the middle of a very long boardroom table. It is no wonder that the people at the either end of table are complaining that the voices at the far end of the call are muffled and muddy.
Tips for Proper Placement
There are simple tools that will help you determine the proper placement of ceiling speakers to ensure everyone can properly hear the far end with the best speech intelligibility. A meeting room is only as good as the sum of its parts and better conferencing sound is only achieved when microphones, acoustics and loudspeaker placement are considered equally.
Consider the Dispersion Pattern
John Ellis from the Shure UK Systems Group explains that there needs to be more attention paid to proper loudspeaker placement to get the best performance: “When designing a new meeting space, video conferencing suite or huddle room, it is important to consider the dispersion pattern of the ceiling loudspeakers you are using. Most ceiling speakers have a dispersion pattern between 90 – 100 degrees conical, which isn’t very wide when its only 2.8 metres above floor level. This distance is fine if you are directly underneath the speaker, but if you are a few metres off axis it will become difficult to hear the high frequencies of the speaker’s voice and their audio will sound muffled and hard to hear clearly. If the correct amount of loudspeakers are not installed in the right positions to cover the room you may have some areas that are very loud and some that are soft; some areas will have more bass and less HF, depending on how bright the room is. Audio below 200 hertz is omnidirectional and as the sound travels up towards higher frequencies the dispersion gets a lot narrower. So off axis the high frequencies roll off before low frequencies which will result in a loss in speech intelligibility and detail to those areas that are not under the loudspeaker.
Know the Size of the Room
Lower ceiling heights equate to speakers with less coverage in the room, which will create hot and cold spots of strong and weak sound, respectively. Thus, more loudspeakers will be required for good coverage, which could be smaller units. John explains that there is an easy way to solve this problem: “EASE Address (http://address.afmg.eu/) is a free software application that will help you determine the best placement of your loudspeakers based on the size of the room, the ceiling height and the number of chairs around the table. All manufactures should provide EASE data with their ceiling speakers. The software will give you the loudspeaker coverage areas in two dimensions and show the hot and cold zones in the room.
Choose the Right Speaker
John also explains that it is important to choose the proper ceiling speaker for the job: “Many of the inexpensive ceiling speakers are designed for corridors or office for basic paging audio, not high quality speech or music applications. Just recently I was in a high-end boardroom, yet looking in the ceiling the speakers were low quality open backed unit. All ceiling loudspeakers should be fully enclosed with back cans that are usually fire rated. This stops dust and dirt ingress, improves sound quality, stops the speakers from rattling or vibrating the ceiling and maintains the fire rating of the ceiling.
“Poor loudspeaker placement can effect that quality of the room’s echo reduction and acoustic Echo Cancellation processing. If you have microphones under a loudspeaker and others off axis, with improper coverage, the signal will not effectively trigger the AEC so that it can determine the appropriate sounds to cancel and mute. Furthermore, this also ties into the argument of using high quality mics for enhanced video conferencing intelligibility.”
For more information about Shure products for meeting rooms, visit shure.com/americas/microflex-advance.
Editor’s Note: This article was originally published by Shure UK in their blog, Sound Hub.