keras/src/layers/preprocessing/audio_preprocessing.py/MelSpectrogram/_dbscale
class MelSpectrogram:    def _dbscale(self, inputs):
        log_spec = 10.0 * (
            self.backend.numpy.log10(
                self.backend.numpy.maximum(inputs, self.min_power)
            )
        )
        ref_value = self.backend.numpy.abs(
            self.backend.convert_to_tensor(self.ref_power)
        )
        log_spec -= 10.0 * self.backend.numpy.log10(
            self.backend.numpy.maximum(ref_value, self.min_power)
        )
        log_spec = self.backend.numpy.maximum(
            log_spec, self.backend.numpy.max(log_spec) - self.top_db
        )
        return log_spec