Introduce unit enums for sound pressure

[epenet]

Breaking change

FOR DEVELOPPERS ONLY: as of Home Assistant Core 2023.1, the following unit constants are deprecated and replaced
by a corresponding enum:

• UnitOfSoundPressure enumerator replaces SOUND_PRESSURE_** constants

Proposed change

Introduce unit enums for sound pressure

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request: Add more units deprecation to blog post developers.home-assistant#1569

Checklist

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[epenet]

Adjusted based on home-assistant/architecture#837 (comment)

[parautenbach]

Nothing wrong with this, but just adding some extra info.

dBA is also acceptable (also noted in the Wikipedia page). Common usage (from what I've seen) is dBA over dB(A). Definitely not dBa.

For a really comprehensive list of dB variants see https://en.wikipedia.org/wiki/Decibel.

A second thing (which probably displays my lack of knowledge around unit management in HA) is this:
Can units have properties, e.g. so that the unit is dB, but there's an attribute/property to say it uses A-weighted values?

dBA, dBB, and dBC
These symbols are often used to denote the use of different weighting filters, used to approximate the human ear's response to sound, although the measurement is still in dB (SPL). These measurements usually refer to noise and its effects on humans and other animals, and they are widely used in industry while discussing noise control issues, regulations and environmental standards. Other variations that may be seen are dBA or dB(A). According to standards from the International Electro-technical Committee (IEC 61672-2013)[52] and the American National Standards Institute, ANSI S1.4,[53] the preferred usage is to write LA = x dB. Nevertheless, the units dBA and dB(A) are still commonly used as a shorthand for A‑weighted measurements. Compare dBc, used in telecommunications.

[epenet]

As you said, the current variant dBa isn't really valid.
I prefer dB(A) over dBA because I think it makes it clearer it's added information.

[emontnemery]

Thanks, @epenet 👍

[frenck]

I would say dBA is significantly more common.

[frenck]

Thanks, @epenet 👍