Review: (little) Noise Level Meter Kit

Contrary to what is suggested in the manual, I prefer to bend the leads of the 4 LEDS at the same angle before soldering them -- it seems easier to me to do it that way than afterwards, But this is just a question of taste, or perhaps your skill with the tweezers; apart from that, the contents of the manual are very above average.

Having passed the soldering exercise, what's left to do is see if it works. The manual gives very precise instructions as to what to do if it does not work first time.

Even though it’s not a true measuring instrument, because it doesn’t give numeric values, this kit works quite well, without any calibration. As soon as it is switched on, it gives on its four LEDs a good indication of the level of environmental noise. The working of the circuit is explained well in the manual, which also gives a complete schematic.

The base mode shows the level of sound in the environment, between 70 dB(A) and 100 dB(A), using the four LEDs which light up one after the other when the volume passes certain limits. A plug in jumper strap allows you to discover three additional modes of working, very well documented in the manual. These modes are a chaser light, the speed of which depends on the volume, a disco light which follows the beat of the music, and a 4-step counter incremented by your hand claps.

Without being spectacular, these playful modes are worthy of study and will arouse interest and lead to questions about the treatment of sound waves with electronic circuits. The manual devotes a few pages to the rudiments of the measurement of sound pressure. This makes the kit an excellent educational tool.

If you look closely at the photo of the printed circuit board above you will notice, opposite where the LEDs are, four unused additional outputs. These are extensions to which you can connect other LEDs or even control circuits for higher power displays. The manual gives several instructions on this subject.

This is a nice surprise even if it’s not the LCD display that the photo on the box led you to believe, but understand that at this price, it’s simply a “trompe-l'oeil” or skeuomorphic as Apple would say. .

After this fulsome praise, I conclude on a critical note: there is nothing in the manual about the microcontroller package – HT46F47, a Taiwanese chip and not well known in these parts. This choice and above all the total absence of open code take the shine off the educational possibilities of this sound meter kit, and definitely are the weak point.