we can hear you, loud and clear

As I wrote earlier this summer, our engineers have worked hard to design the optimal public address system for your new vivastations.  Here’s what the system will include, and how good it’s going to sound.

Most PA systems are pretty frustrating in the garbled sound quality they provide.  We knew we wanted to do much better.  There’s nothing worse than knowing something important is being said, but not being able to understand it.

To make sure the new PA system is always audible, we started with an acoustic analysis study using special “Enhanced Acoustic Simulator for Engineers” (EASE) software. This study analyzed the two elements most critical to sound: Sound Pressure Level (SPL) and Speech Transmission Index (STI). The SPL, measured in decibels (dB), is concerned with sound magnitude and takes into account ambient noise levels – it is the relative “loudness” of a sound.  STI predicts how the equipment being used and the surrounding environment will affect the quality of the sound, and therefore how intelligible it is for you as you hear it.

First, the acoustic engineers needed to determine what effects our curved canopies and the beams and angles inside the station would have on the way sound is going to move around.  Secondly, the reflection of sound by the concrete wall, floor and glass was modeled. This analysis helped predict how clear the final sound will be on the platform and in the enclosure, and also helped determine the number and placement of speakers that will be most effective in achieving clear sounds.

Following this sophisticated modeling the engineers determined that the optimal number of speakers to achieve our goals would be 12 speakers located outside of the passenger enclosure, and another 3 speakers inside.

The next challenge was to work on the volume to be used by the speakers.  The problem with PA systems in noisy places is that the ambient noise can overwhelm the volume of the PA system, making it impossible to hear what’s being said.  Our solution is to use a speaker volume system that automatically adjusts when its sensors detect that the ambient noise has increased or decreased.

There are two sensors on each viva platform to measure noise level. This way, announcements should be audible whether there’s a bus idling in the station and trucks are moving past, or it’s nighttime and quiet.

The PA system will be used for recorded and live announcements from transit operations, such as emergency information or service changes, but will not announce bus arrivals although it does have that capability.

Although we’ve tested the system many times, we continue to monitor the sound levels now that operations have started.  We hope you have been out to test drive the first section of rapidways now open on Highway 7 and let us know if you can truly hear us, loud and clear.