Simple and easy to do using an empty ambient deodorant,increases the sound more than 20 decibels without battery nor wires

Step 1: Materials and Tools to Make It

A deodorant tin can can,not the aluminum one,and to cover it some kind of adhesive sheet,like this ( carbon fiber),or simply paint it

Step 2: Preparing the Can

Take off the upper part part of the can,with the help of a plier or screwdriver

Step 3: Getting the Components of the Amplifier

With a handsaw or a angle grinder Cut both sides of the can,the upper one will be the base and the lower one will be a sound reflector

Step 4: Prepparing the Components

Bend a little bit the bottom side,in order to let us introduce in the can,and with the help of a hammer bend the upper side as seen on picture,this will make a better seat of the can on the base
Also we have to mark a rectangule according to the size of our cell to let us put it in,make the little window some mm bigger so the cell enters freely

Step 5: Finishing the Job

And after soldering the base and the sound reflector in the inside,I covered It with fiber carbon sheet ,It is a really efficient amplifier,It amplifies enought the sound of the cell