Extended Hoth noise and Aerial Simulation

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Hoth noise

Hoth noise is a random noise that has a power density spectrum corresponding to that published by Hoth. It is defined as a simulated room noise in ITU-T P.800. P.800 defines the power density spectrum of the Hoth noise between 100 Hz and 8000 Hz with the band edges conforming to the filters described in IEC 61260 (Octave-band and fractional-octave-band filters).

Extended Hoth noise

The upper edge of the power density spectrum of the Hoth noise is extended in order to simulate wide-band room noise. The extended slope of the spectrum is -15 dB/oct.

Sample programs

Generation of extended Hoth noise

hoth.m

This is a sample Matlab/Octave program to generate an extended Hoth noise. Note that the lower edge of the spectrum does not conform to the IEC61260 standard, because of the FIR filter implementation.

Aerial Simulation

aerial_attack.m

This is a sample Matlab/Octave program to simulate an aerial transmission in a room. It includes a series of signal processings as follows:

• Convolving the room impulse response (reverberation time of 0.4 s, direct-to-reverberant energy ratio of 3.6 dB) to the stego signal.
  imp_spk_room_mic.txt(CRLF; impulse response file)
• Additive extended Hoth noise (extends the highest frequency from 8 kHz to 22.05 kHz) at −36 dB to the convolved stego signl
• Linear speed change conversion (pitch and time-scale conversion) of −0.1 %

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