Except finding '-45 dB' is frustratingly common. Have a look at this random microphone datasheet from DigiKey: https://www.sameskydevices.com/product/resource/cmm-3125at-4...
They do state the test conditions "at 94 dB SPL, 1 kHz", but don't specify the units attacked to the actually measurement. It's given as a ratio to an unspecified quantity.