Evaluating a New Algorithm for Multi-Talker Babble ...

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Overview: ➢ Performance with a cochlear implant (CI) in noise is generally poor. ➢ Previous noise reduction techniques tend to work poorly in non-stationary ...
Evaluating a New Algorithm for Multi-Talker Babble Noise Reduction Using Q-Factor Based Signal Decomposition Roozbeh Soleymani, Ivan W. Selesnick, Natalia Stupak, David M. Landsberger Overview:  Performance with a cochlear implant (CI) in noise is generally poor.  Previous noise reduction techniques tend to work poorly in non-stationary noise (e.g., multi-talker babble).  We propose a new algorithm to improve speech in multi-talker babble that could be implemented into a speech processor.  Results demonstrate a consistent and significant benefit in intelligibility and sound quality.

Evaluation Methods: Noise Free Speech HQF Component

Noise Free Speech LQF Component

Figure 1. Waveforms of the noise free,

LQF, HQF components.

their LQF, HQF components.

HQF : High Q-Factor LQF : Low Q-Factor

HQF : High Q-Factor LQF : Low Q-Factor

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Noisy Speech LQF Component

Time (Sec.)

𝑄=

- Added noise is 6-Talker babble, SNR=0dB - Each graph number corresponds to a block in block diagram Figure 3.

A pulse with a high Q-factor (HQF) exhibits more sustained oscillatory behavior. A pulse with a low Q-factor (LQF) exhibits less sustained oscillatory behavior.

SNR Estimation

Noisy Speech HQF Component

Noisy Speech

Noisy Speech Cleaned HQF

Output Processed Speech

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Noise Free Speech HQF Component

Noisy Speech LQF Component

Noisy Speech HQF Component

Noisy Speech LQF Component

 Subjects: 7 Advanced Bionics Fidelity 120 or Optima users with Medium Clear Voice.  Stimuli: IEEE sentences in multi-talker babble SNR 0, 3, 6, or 9dB, Processed or Unprocessed  Evaluating Intelligibility: Words correct were measured for 20 sentences for each of the 8 conditions (two processing conditions and 4 SNRs) in a randomized order.  Evaluating Quality: A MUshra test was used to determine sound quality for all 8 conditions relative to a speech in quiet reference. The low quality anchor was 6-talker babble noise without speech. The process was repeated for 5 sentences. Results: For all subjects, intelligibility and quality improved. Intelligibility improves 10 to 30% in 6-talker babble. Sound Quality improves between 15 and 30 points. Conclusions: The new algorithm might greatly improve performance in realistic noisy environments (i.e. a cocktail party). We are working on implementing a real time implementation of the new algorithm.

Noise Free (Clean) Speech

Noisy Speech

Output Processed Speech

Noisy Speech Cleaned HQF

- Time axis (Horizontal) : 0 to 2 (sec) - Freq. axis (Vertical) : 0 to 6000Hz - Added noise is 6-Talker babble, SNR=0dB - Each graph number corresponds to a block in block diagram Figure 3. 0

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OUTPUT

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Results

Improvement found at ALL SNRs

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SNR>12dB

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Noise Free Speech LQF Component

Spectral cleaning and re-composition

Each number in the block diagram corresponds to a plot in figures 1 and 2 signal

Noisy Speech Residual Component

- Time axis (Horizontal) : 0 to 2 (sec)

𝑓𝑐 . 𝐵𝑊

Spectrograms of the noise

free, noisy and de-noised signals and

Noisy Speech LQF Component

What is the Q-factor? The Q-factor of a pulse is defined as the ratio of its center frequency to its bandwidth:

Figure 2.

noisy and de-noised signals and their

Algorithm summary (See Figure 3):  Detect signal to noise ratio to determine how aggressive the de-noising will be.  Decompose signal into three components: a low Q-factor (LQF), high Q-factor (HQF), and residual noise components using a sparse optimization wavelet method. (see “What is the Q-factor?”)  The low Q-factor component is used as a template to further de-noise the high Q-factor component.  The de-noised high Q-factor signal is added to the low Q-factor component to create the de-noised output.

Noise Free (Clean) Speech

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INPUT

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WAVELET SETTING 1

SNR ESTIMATION

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Q FACTOR BASED SIGNAL DECOMPOSITION

WAVELET SETTING 2

LQF HQF

5dB

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