Week 3

This is article from another website about snoring detector

Introduction

The use of polysomnographic recording is a standard evaluation procedure for SRBD patients.

However, it is expensive and is not suitable for long term monitoring. Penzel developed a digital

recording device called MESAM IV, to monitor oxygen saturation, heart rate, snoring, and body

position in order to screen subjects for OSAS . They also indicated that this inexpensive implementation would allow the development of homecare systems for the analysis and long term monitoring of snoring.

The automatic scoring system of MESAM IV calculates oxygen desaturation index (ODI), heart rate variation index (HVI) and intermittent snoring index (ISI) to obtain an apnoea-hypopnoea index (AHI). The snoring sounds are recorded by means of a laryngeal microphone. If the proportion of sounds between 50Hz and 800Hz exceeds 50%, it is assumed that there is snoring. Intermittent snoring is defined as intervals between two detected snores longer than 5 seconds and shorter than 60 seconds. Evaluating snoring interval analysis on 68 patients with all degrees of obstructive sleep apnea, Penzel et al[6]. reported that correlation between snoring interval analysis and polysomnographically scored apneas was moderate (r=0.51) . Following this development, a number of validation studies on MESAM IV were presented [7-

11]. In those studies, the intermittent snoring index was found to have high sensitivity (92%-96%) but low specificity (16%-27%).

Diagram 1 : Structure of snore detector

Figure 1 : The prototype of snoring detector.

Below are the signal of snoring detector

Figure 2: Original signal taken by a microphone and A/D converter at 2kHz

Figure 3 : The reference voltage is set to zero, and all signals are set to have positive voltage

Figure 4: Extraction of the profile by finding the maximum voltage value in every 10 points (200Hz)

Figure 5: 10-points sum to amplify the peaks (20Hz)

Figure 6 : 10-point moving average to smooth the curve

Figure 7 : Sample data of snores and intermittent snores detection

 

Table 1 : Evaluation of the snoring detector in a lab environment

 

Table 2 : Evaluation of the snoring detector in a home environment