Audible alarm options

In my project, I’m using a piezo buzzer (80db, 4kHz, 3-16VDC, 7mA) for an audible alarm, which is driven by an AVR mcu pin. The mcu is running at 5V and I understand its pin can source 20mA. I’m looking for ideas to create a louder alarm. It would be nice if I could make the volume and frequency configurable options since I’ve noticed that a few older guys could not hear the current buzzer’s 4kHz frequency.

Playing around on a breadboard I’ve noticed that I can increase the volume with a higher voltage so that’s one option. I have either 12-14V external power or a 9V internal battery so I could drive the buzzer with that voltage using a transistor connected to the mcu. What are some other options I should consider? I’m a software guy with only basic hardware experience so feel free to construct any response for a hardware novice. Thanks

A piezo siren. You can buy them at most electronic retailers. This particular one would sound like a car alarm. 100dB at 1 metre.

Thanks. I'll look for some piezo siren options. Would there be a simple way to control the volume with a mcu? I'd like to be able to configure low/med/high volume options.

Usually piezo buzzer datasheets have a graph showing the frequency response of the buzzer - the rated frequency of the buzzer is the point on the graph which has the highest frequency response. If you drive the buzzer at another frequency, the volume will go down, although it will sound different at a different frequency.

Thanks. I've seen the frequency response curve on datasheets for external drive buzzers. I'm not really sure what it takes to drive that kind with a mcu but I'll investigate and see if that could be my solution. Right now, I'm using a buzzer with an internal drive so I just set a mcu pin high to sound the alarm.

One suggestion for simply making it louder would be to drive it with a transistor switched by the pin, instead of directly powering it.