This character is a Other Symbol and is commonly used, that is, in no specific script. The character is also known as sound off.
The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. U+1F56B offers a line break opportunity at its position, except in some numeric contexts.
The Wikipedia has the following information about this codepoint:
A megaphone, speaking trumpet, bullhorn, blowhorn, or loudhailer is usually a portable or hand-held, cone-shaped acoustic horn used to amplify a person's voice or other sounds and direct it in a given direction. The sound is introduced into the narrow end of the megaphone, by holding it up to the face and speaking into it, and the sound waves radiate out the wide end. A megaphone increases the volume of sound by increasing the acoustic impedance seen by the vocal cords, matching the impedance of the vocal cords to the air, so that more sound power is radiated. It also serves to direct the sound waves in the direction the horn is pointing. It somewhat distorts the sound of the voice because the frequency response of the megaphone is greater at higher sound frequencies.
Since the 1960s the voice-powered acoustic megaphone described above has been replaced by the electric megaphone, which uses a microphone, an electrically-powered amplifier and a folded horn loudspeaker to amplify the voice.