The problem with using decibels is that since it is a relative unit you need to know what it is relative to, and that is often not just the unit but also the quantity. Unfortunately, this part is (as expressed) at times omitted or put in the wrong place. And its often also the engineers in the respective fields that keep using this incorrect notation spreading the confusion for those outside the domain.

E.g., acoustic engineers often write db(A) for A-weighted sound pressure levels. Yes, it is often noted this way, but it is incorrect. The correct way is to specify the quantity and that the quantity is A-weighted, `L_{p, A} = 80 dB` for example to express an A-weighted sound pressure level of 80 dB.

Regarding sound pressure and sound power. Sound power is not expressed using A-weighting because it does not make sense. Sound power is a property of the source. A-weighting is a property of the receiver, that is, the human listener.

> The problem with using decibels is that since it is a relative unit you need to know what it is relative to

Ye but that is also the point. The author seem to prefer to memorize dozens of absolute values.