Increase frequency of beeps to improve loudness

[kevinjwalters]

There's an observation in Pimoroni Forums: Grow kit feedback

The piezo alarm is, in my opinion, very quiet. I will definitely not notice it chirping about dry soil from the other side of our busy kitchen.

I don't have an unboxed grow board to test this with but I suspect you are using a small piezo buzzer which performs at higher frequencyes (2-3 kHz) in terms of loudness but the code currently shows a liberal sprinkling of 440Hz. That's a useful referernce (A4) but may not be a good choice for producing a beep that's audible at a distance even with its square wave harmonics.

https://github.com/pimoroni/grow-python/blob/bc5fec56c69fdef26f9f47660df3d892a377a04c/examples/monitor.py#L786

And

https://github.com/pimoroni/grow-python/blob/bc5fec56c69fdef26f9f47660df3d892a377a04c/library/grow/__init__.py#L14

https://github.com/pimoroni/grow-python/blob/bc5fec56c69fdef26f9f47660df3d892a377a04c/library/grow/__init__.py#L45

Those two could also be a single variable rather than two independent values.

I don't know if there's already use of different perodic beeping to indicate different emergency conditions but frequency could also be a part of this using the frequency to effectively increase volume, i.e. as it gets drier beep at 550, 1100, 2200Hz.

[tomgidden]

For what it's worth, I tried changing the frequencies a LOT, but it didn't make much difference. I too thought it would just be a matter of finding the right frequency for the particular sounder.

Saying that, my 9yo kid could hear the (default) beeping from across the room.

[kevinjwalters]

My recollection is you can barely here C3 (263.74) on a transistor amped 5mm speaker but C6 and C7 are strangely loud at least in a relative sense. The Adafruit CLUE has this setup on the reverse-side of the board.

• Adafruit CLUE metal detector - venturing outside (YouTube) - higher frequencies on the CLUE audible at a range of around 2m outside
• Adafruit Forums: Speaker issues on CLUE - discussion on frequency range of CLUE speaker vs louder Adafruit Circuit Playground Express (CPX)
• Adafruit Forum: What is the speaker on the Circuit Playground Express? - discussion about the larger (amplifier-driven) 7.5mm speaker on CPX including data sheet frequency response of a similar speaker

The CUI CMT-0503-75-SMT-TR might be comparable, the frequency response from datasheet is shown below:

These devices often have a resonant frequency where it gets very loud. I'm not sure if it's healthy for the device to deliberately use that.