sound power of a source - the total sound energy radiated by the source per unit of time. The common unit is the erg per second, but the power may also be expressed in watts., sound power level - ... 10Log(P/PO) in decibels where P = the sound power, PO = the reference sound power of 10 to power -12 watt (i.e. 1 picowatt), and Log = Logarithm to base 10, the logarithm of the ratio of a given sound power to the reference sound power. Power level in decibels is ten times the logarithm to the base ten of the ratio., heli võimsus - helienergia, mida heliallikas kiirgab ajaühikus. Ühik: vatt (W), tähis W., heli võimsustase - antud helivõimsuse ja standardse nullnivoo suhte logaritm kindlas sagedusribas või kindlal sageduskarakteristikul. Standardne nullnivoo pn 1 pW. Ühik: bell (B), tähis Lw (w lugeda alapaigutusega).