In a way, everyone knows what hearing aids are - they're things that people put into their ears to improve their hearing. But what are they? If you were to assume they were devices that simply made incoming noise louder, then you'd be selling them short. A device that simple is known as a PSAP, or "personal sound amplification product." These certainly make sound louder, but could also damage your hearing further. They're commonly found in pharmacies and for purchase online.