def _hertz_to_mel(self, frequencies_hertz):
        """Converts frequencies in `frequencies_hertz` in Hertz to the
            mel scale.

        Args:
            frequencies_hertz: A tensor of frequencies in Hertz.
            name: An optional name for the operation.

        Returns:
            A tensor of the same shape and type of `frequencies_hertz`
            containing frequencies in the mel scale.
        """
        return _MEL_HIGH_FREQUENCY_Q * self.backend.numpy.log(
            1.0 + (frequencies_hertz / _MEL_BREAK_FREQUENCY_HERTZ)
        )
Converts frequencies in `frequencies_hertz` in Hertz to the
            mel scale.

        Args:
            frequencies_hertz: A tensor of frequencies in Hertz.
            name: An optional name for the operation.

        Returns:
            A tensor of the same shape and type of `frequencies_hertz`
            containing frequencies in the mel scale.
        
keras/src/layers/preprocessing/mel_spectrogram.py