**3. Experimental Results and Analysis**

The performance was evaluated on recorded sound-event signals in a low noisy environment at 20 signal-to-noise ratios (SNRs). The sound-event database had a total of 500 recorded signals containing four event classes: speech (SP), door open (DO), door knocking (DK), and footsteps (FS). An overview of the experimental setup is given as the following: all signals had a 16-bit resolution and a sampling frequency of 44.1 KHz. A 2048 length of Hanning window with 50% overlap was used for signal processing. Nonlinear SVM with a Gaussian RBF kernel was used for constructing the MSVM learning model. Other kernels such as polynomials, sigmoid, and even linear function were tested, but the best performance was delivered by the Gaussian kernel. A 4-fold cross-validation strategy was used in the training phase for tuning the classifier parameters when using 80% of the recorded signals (n = 400) from the sound-event database.

The performance of the proposed noisy sound separation and event classification (NSSEC) method was demonstrated and presented into the following two sections: (1) the separating performance, and (2) the MSVM classifier.

### *3.1. Sound-Event Separation and Classification Performance*

Event mixtures consist of two sound-event signals in low noisy environment at 20 dB SNRs. A hundred sound-event signals of four classes were randomly selected and then mixed to generate 120 mixtures of six types (i.e., DO + DK, DO + FS, DO + SP, DK + FS, DK + SP, and FS + SP). The separation performance measured the signal-to-distortion ratio (SDR) (i.e., *SDR* <sup>=</sup> <sup>10</sup> *log*10 *starget* 2/ *einter f* + *enoise* + *earti f* 2 where *einter f* , *enoise*, and *earti f*). The SDR represents the ratio of the magnitude distortion of the original signal by the interference from other sources. The proposed separation method was compared with the state-of-the-art NMF approach (i.e., CMF [38], NMF-ISD [14,39], and SNMF [40–42] methods). The cost function was the least squares with 500 maximum number of iterations.
