In my personal opinion, we need more “blended” voice-evac/horn systems that actually take into account ambient noise levels. For example, in a school a history classroom wouldn’t have nearly the same ambient noise level as a woodshop; just the same with an auditorium and a gymnasium. Voice-evacuation is perfect for areas where there may be a large concentration of people in a relatively small space (like a history classroom or an auditorium), and can reduce levels of panic or anxiety that come with hearing a startling horn. In areas like a woodshop, however, a fairly quiet speaker could go unnoticed for a long period of time. In those scenarios, horns or bells provide the most effective sound output. Of course, you could install audio boosters or use alternative speakers as opposed to horns, but why spend the extra money when you could just install a horn? Then there’s the whole issue of language and instruction. No matter where you’re from, a loud screech or buzz means get out, whereas a nice man telling you calmly to leave the building might be harder to decipher if you don’t know English. Code requirements should be adjusted to give schools (and other buildings, for that matter) more leeway with regards to installing horns. Just because a building has voice-evac doesn’t make it safer; and I’d argue that a building that knows where to use both where appropriate probably does it the best of all.
This is not entirely true. Loud screeches and buzzes can come from almost anything that could indicate something is wrong. I almost always associate loud buzzing sounds with an automatic door closing or something coming at me (i.e. store lifts) because of my past experiences. I’m familiar with piezos because I’ve been in a school that uses them for over two years.
One of the dominant signals in Japan to signify an [color=transparent]earthquake (I’ll let you guess after listening) via a television broadcast is a fancy little sequence of chimes. We have no such thing in the US, and without any context or past experience we would have no such idea what the heck those creepy chimes are supposed to indicate.
Fire alarms are only as good as their familiarity, which is why voice evacuation systems have a much higher advantage for those without any knowledge of a building’s fire alarm system. Those who do speak English may be able to assist others by providing context clues or assistance as needed.
To answer the OP’s question, current draw involves some simple maths (except it can get a bit complicated when you’re dealing with multiple models and volume settings). This is measured in watts, which is the rate of energy transfer between two systems.
Suppose I am working with a Potter EVAX 200 for a school, which is capable of providing up to 200 watts of power to a NAC, a set of Wheelock E50s, which outputs 88 dBs when set to 2 watts power, and a set of STH-15S, which outputs 90 dBs when set to 0.94 watts of power. Note that each of the NAs have adjustable outputs, so it’s important to make sure to change the numbers to reflect their settings.
The total number of watts required must NOT exceed a panel’s capable output. We can find if the number of each devices does not exceed the limit by an inequality:
My opinion in voice evac is that they are good if they are in the area that I am in so if the fire alarm goes off it doesn’t make me jump out of my skin but when I watch fire alarm videos on YouTube, I want there to be systems that have all horns instead.
To tell you the truth, I prefer horns only because I grew up with them. I didn’t attend a school with voice evac until college.
I don’t see a ton of voice evac. systems, as it’s only required in Canada if your building is 14 stories or higher. I have seen a few mixed systems, where they have horns/bells throughout, and a paging system as well.