**Figure 2.**
Healthy EID (EID with a healthy rear bearing).

**Figure 2.**
Healthy EID (EID with a healthy rear bearing).

**Figure 3.**
EID with 15 broken rotor blades (indicated by yellow circle).

**Figure 3.**
EID with 15 broken rotor blades (indicated by yellow circle).

**Figure 4.**
EID with a bent spring (indicated by yellow circle).

**Figure 4.**
EID with a bent spring (indicated by yellow circle).

**Figure 5.**
EID with a shifted brush (indicated by yellow circle).

**Figure 5.**
EID with a shifted brush (indicated by yellow circle).

**Figure 6.**
EID with a rear ball bearing fault (indicated by yellow square).

**Figure 6.**
EID with a rear ball bearing fault (indicated by yellow square).

**Figure 8.**
CG-A with a heavily damaged rear sliding bearing (indicated by yellow circle).

**Figure 8.**
CG-A with a heavily damaged rear sliding bearing (indicated by yellow circle).

**Figure 9.**
CG-A with a damaged shaft and heavily damaged rear sliding bearing (indicated by yellow circle).

**Figure 9.**
CG-A with a damaged shaft and heavily damaged rear sliding bearing (indicated by yellow circle).

**Figure 10.**
Motor off (CG-A off).

**Figure 10.**
Motor off (CG-A off).

**Figure 12.**
CG-B with a light damaged rear sliding bearing (indicated by yellow circle).

**Figure 12.**
CG-B with a light damaged rear sliding bearing (indicated by yellow circle).

**Figure 13.**
Motor off (CG-B off).

**Figure 13.**
Motor off (CG-B off).

**Figure 14.**
Developed acoustic based approach.

**Figure 14.**
Developed acoustic based approach.

**Figure 15.**
(**a**) Capacity microphone, computer and electric impact drill. (**b**) Measurement of acoustic signals.

**Figure 15.**
(**a**) Capacity microphone, computer and electric impact drill. (**b**) Measurement of acoustic signals.

**Figure 16.**
Block diagram of the developed method MSAF-17-MULTIEXPANDED-FILTER-14.

**Figure 16.**
Block diagram of the developed method MSAF-17-MULTIEXPANDED-FILTER-14.

**Figure 17.**
Difference (|**h** − **f**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 17.**
Difference (|**h** − **f**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 18.**
Difference (|**h** − **s**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 18.**
Difference (|**h** − **s**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 19.**
Difference (|**f** − **s**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 19.**
Difference (|**f** − **s**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 20.**
Difference (|**b** − **h**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 20.**
Difference (|**b** − **h**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 21.**
Difference (|**b** − **s**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 21.**
Difference (|**b** − **s**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 22.**
Difference (|**b** − **f**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 22.**
Difference (|**b** − **f**|) using the MSAF-17-MULTIEXPANDED-FILTER-14 method.

**Figure 23.**
Values of features of healthy EID (145 features, seven frequency bandwidths, <271–287 Hz>, <450–490 Hz>, <550–565 Hz>, <2290–2324 Hz>, <11091–11118 Hz>, <11183–11220 Hz>, <11232–11253 Hz>).

**Figure 23.**
Values of features of healthy EID (145 features, seven frequency bandwidths, <271–287 Hz>, <450–490 Hz>, <550–565 Hz>, <2290–2324 Hz>, <11091–11118 Hz>, <11183–11220 Hz>, <11232–11253 Hz>).

**Figure 24.**
Values of features of the EID with 15 broken rotor blades (faulty fan) (145 features, seven frequency bandwidths, <271–287 Hz>, <450–490 Hz>, <550–565 Hz>, <2290–2324 Hz>, <11091–11118 Hz>, <11183–11220 Hz>, <11232–11253 Hz>).

**Figure 24.**
Values of features of the EID with 15 broken rotor blades (faulty fan) (145 features, seven frequency bandwidths, <271–287 Hz>, <450–490 Hz>, <550–565 Hz>, <2290–2324 Hz>, <11091–11118 Hz>, <11183–11220 Hz>, <11232–11253 Hz>).

**Figure 25.**
Values of features of the EID with a bent spring (145 features, seven frequency bandwidths, <271–287 Hz>, <450–490 Hz>, <550–565 Hz>, <2290–2324 Hz>, <11091–11118 Hz>, <11183–11220 Hz>, <11232–11253 Hz>).

**Figure 25.**
Values of features of the EID with a bent spring (145 features, seven frequency bandwidths, <271–287 Hz>, <450–490 Hz>, <550–565 Hz>, <2290–2324 Hz>, <11091–11118 Hz>, <11183–11220 Hz>, <11232–11253 Hz>).

**Figure 26.**
Values of features of the EID with a rear ball bearing fault (145 features, seven frequency bandwidths, <271–287 Hz>, <450–490 Hz>, <550–565 Hz>, <2290–2324 Hz>, <11091–11118 Hz>, <11183–11220 Hz>, <11232–11253 Hz>).

**Figure 26.**
Values of features of the EID with a rear ball bearing fault (145 features, seven frequency bandwidths, <271–287 Hz>, <450–490 Hz>, <550–565 Hz>, <2290–2324 Hz>, <11091–11118 Hz>, <11183–11220 Hz>, <11232–11253 Hz>).

**Figure 27.**
Values of features of the healthy CG-A (29 features, two frequency bandwidths, <515–537 Hz>, <1560–1575 Hz>).

**Figure 27.**
Values of features of the healthy CG-A (29 features, two frequency bandwidths, <515–537 Hz>, <1560–1575 Hz>).

**Figure 28.**
Values of features of the CG-A with a heavily damaged rear sliding bearing (29 features, two frequency bandwidths, <515–537 Hz>, <1560–1575 Hz>).

**Figure 28.**
Values of features of the CG-A with a heavily damaged rear sliding bearing (29 features, two frequency bandwidths, <515–537 Hz>, <1560–1575 Hz>).

**Figure 29.**
Values of features of the CG-A with a damaged shaft and heavily damaged rear sliding bearing (29 features, two frequency bandwidths, <515–537 Hz>, <1560–1575 Hz>).

**Figure 29.**
Values of features of the CG-A with a damaged shaft and heavily damaged rear sliding bearing (29 features, two frequency bandwidths, <515–537 Hz>, <1560–1575 Hz>).

**Figure 30.**
Values of features of the healthy CG-B (43 features, three frequency bandwidths, <94–109 Hz>, <194–207 Hz>, <463–488 Hz>).

**Figure 30.**
Values of features of the healthy CG-B (43 features, three frequency bandwidths, <94–109 Hz>, <194–207 Hz>, <463–488 Hz>).

**Figure 31.**
Values of features of the CG-B with a light damaged rear sliding bearing (43 features, three frequency bandwidths, <94–109 Hz>, <194–207 Hz>, <463–488 Hz>).

**Figure 31.**
Values of features of the CG-B with a light damaged rear sliding bearing (43 features, three frequency bandwidths, <94–109 Hz>, <194–207 Hz>, <463–488 Hz>).

**Table 1.**
RMS values of the healthy EID.

**Table 1.**
RMS values of the healthy EID.

Number of Samples | RMS Value | Number of Samples | RMS Value |
---|

x_{RMS1} | 0.237122 | x_{RMS5} | 0.240819 |

x_{RMS2} | 0.231192 | x_{RMS6} | 0.236356 |

x_{RMS3} | 0.234878 | x_{RMS7} | 0.239650 |

x_{RMS4} | 0.238282 | x_{RMS8} | 0.238406 |

**Table 2.**
RMS values of the EID with 15 broken rotor blades (faulty fan).

**Table 2.**
RMS values of the EID with 15 broken rotor blades (faulty fan).

Number of Samples | RMS Value | Number of Samples | RMS Value |
---|

x_{RMS51} | 0.322252 | x_{RMS55} | 0.312347 |

x_{RMS52} | 0.316197 | x_{RMS56} | 0.318529 |

x_{RMS53} | 0.317383 | x_{RMS57} | 0.310883 |

x_{RMS54} | 0.305535 | x_{RMS58} | 0.302719 |

**Table 3.**
RMS values of the EID with a bent spring.

**Table 3.**
RMS values of the EID with a bent spring.

Number of Samples | RMS Value | Number of Samples | RMS Value |
---|

x_{RMS101} | 0.250579 | x_{RMS105} | 0.245578 |

x_{RMS102} | 0.244888 | x_{RMS106} | 0.243813 |

x_{RMS103} | 0.244461 | x_{RMS107} | 0.246395 |

x_{RMS104} | 0.249611 | x_{RMS108} | 0.246297 |

**Table 4.**
RMS values of the EID with a shifted brush.

**Table 4.**
RMS values of the EID with a shifted brush.

Number of Samples | RMS Value | Number of Samples | RMS Value |
---|

x_{RMS151} | 0.006427 | x_{RMS155} | 0.006478 |

x_{RMS152} | 0.006338 | x_{RMS156} | 0.007226 |

x_{RMS153} | 0.008981 | x_{RMS157} | 0.007020 |

x_{RMS154} | 0.009021 | x_{RMS158} | 0.006644 |

**Table 5.**
RMS values of the EID with a rear ball bearing fault.

**Table 5.**
RMS values of the EID with a rear ball bearing fault.

Number of Samples | RMS Value | Number of Samples | RMS Value |
---|

x_{RMS201} | 0.235278 | x_{RMS205} | 0.234696 |

x_{RMS202} | 0.236730 | x_{RMS206} | 0.236078 |

x_{RMS203} | 0.233518 | x_{RMS207} | 0.237600 |

x_{RMS204} | 0.234478 | x_{RMS208} | 0.237778 |

**Table 6.**
RMS values of the healthy CG-A.

**Table 6.**
RMS values of the healthy CG-A.

Number of Samples | RMS Value | Number of Samples | RMS Value |
---|

x_{RMS251} | 0.203343 | x_{RMS255} | 0.209252 |

x_{RMS252} | 0.203521 | x_{RMS256} | 0.215012 |

x_{RMS253} | 0.201109 | x_{RMS257} | 0.209241 |

x_{RMS254} | 0.205511 | x_{RMS258} | 0.205984 |

**Table 7.**
RMS values of the CG-A with a heavily damaged rear sliding bearing.

**Table 7.**
RMS values of the CG-A with a heavily damaged rear sliding bearing.

Number of Samples | RMS Value | Number of Samples | RMS Value |
---|

x_{RMS301} | 0.234359 | x_{RMS305} | 0.234927 |

x_{RMS302} | 0.234860 | x_{RMS306} | 0.233882 |

x_{RMS303} | 0.231783 | x_{RMS307} | 0.235229 |

x_{RMS304} | 0.237120 | x_{RMS308} | 0.229835 |

**Table 8.**
RMS values of the CG-A with a damaged shaft and heavily damaged rear sliding bearing.

**Table 8.**
RMS values of the CG-A with a damaged shaft and heavily damaged rear sliding bearing.

Number of Samples | RMS Value | Number of Samples | RMS Value |
---|

x_{RMS351} | 0.239449 | x_{RMS355} | 0.248779 |

x_{RMS352} | 0.246317 | x_{RMS356} | 0.250027 |

x_{RMS353} | 0.246894 | x_{RMS357} | 0.250791 |

x_{RMS354} | 0.247325 | x_{RMS358} | 0.250203 |

**Table 9.**
RMS values of the healthy CG-B.

**Table 9.**
RMS values of the healthy CG-B.

Number of Samples | RMS Value | Number of Samples | RMS Value |
---|

x_{RMS451} | 0.248146 | x_{RMS455} | 0.248331 |

x_{RMS452} | 0.254812 | x_{RMS456} | 0.259062 |

x_{RMS453} | 0.248951 | x_{RMS457} | 0.263240 |

x_{RMS454} | 0.240446 | x_{RMS458} | 0.264600 |

**Table 10.**
RMS values of the CG-B with a lightly damaged rear sliding bearing.

**Table 10.**
RMS values of the CG-B with a lightly damaged rear sliding bearing.

Number of Samples | RMS Value | Number of Samples | RMS Value |
---|

x_{RMS501} | 0.131587 | x_{RMS505} | 0.103367 |

x_{RMS502} | 0.121155 | x_{RMS506} | 0.095910 |

x_{RMS503} | 0.103567 | x_{RMS507} | 0.108105 |

x_{RMS504} | 0.094650 | x_{RMS508} | 0.105756 |

**Table 11.**
Computed values of E_{D} and TE_{D} of the EID using the MSAF-17-MULTIEXPANDED-FILTER-14 method and the NN classifier.

**Table 11.**
Computed values of E_{D} and TE_{D} of the EID using the MSAF-17-MULTIEXPANDED-FILTER-14 method and the NN classifier.

**Type of Acoustic Signal** | **E**_{D} (%) |

Healthy EID | 100 |

EID with a bent spring | 92 |

EID with (15 broken rotor blades) faulty fan | 100 |

EID with shifted brush (motor off) | 100 |

EID with rear ball bearing fault | 88 |

| **TE**_{D} (%) |

Total efficiency of recognition of the EID | 96 |

**Table 12.**
Computed values of E_{D} and TE_{D} of the EID using the RMS and the NN classifier.

**Table 12.**
Computed values of E_{D} and TE_{D} of the EID using the RMS and the NN classifier.

**Type of Acoustic Signal** | **E**_{D} (%) |

Healthy EID | 56 |

EID with a bent spring | 100 |

EID with (15 broken rotor blades) faulty fan | 100 |

EID with shifted brush (motor off) | 100 |

EID with rear ball bearing fault | 60 |

| **TE**_{D} (%) |

Total efficiency of recognition of the EID | 83.2 |

**Table 13.**
Computed values of E_{CG-A} and TE_{CG-A} of the CG-A using the MSAF-17-MULTIEXPANDED-FILTER-14 method and the NN classifier.

**Table 13.**
Computed values of E_{CG-A} and TE_{CG-A} of the CG-A using the MSAF-17-MULTIEXPANDED-FILTER-14 method and the NN classifier.

**Type of Acoustic Signal** | **E**_{CG-A} (%) |

Healthy CG-A | 100 |

CG-A with a heavily damaged rear sliding bearing | 100 |

CG-A with a damaged shaft and heavily damaged rear sliding bearing | 88 |

Motor off | 100 |

| **TE**_{CG-A} (%) |

Total efficiency of recognition of the CG-A | 97 |

**Table 14.**
Computed values of E_{CG-A} and TE_{CG-A} of the CG-A using the RMS and the NN classifier.

**Table 14.**
Computed values of E_{CG-A} and TE_{CG-A} of the CG-A using the RMS and the NN classifier.

**Type of Acoustic Signal** | **E**_{CG-A} (%) |

Healthy CG-A | 100 |

CG-A with a heavily damaged rear sliding bearing | 92 |

CG-A with a damaged shaft and heavily damaged rear sliding bearing | 92 |

Motor off | 100 |

| **TE**_{CG-A} (%) |

Total efficiency of recognition of the CG-A | 96 |

**Table 15.**
Computed values of E_{CG-B} and TE_{CG-B} of the CG-B using the MSAF-17-MULTIEXPANDED-FILTER-14 method and the NN classifier.

**Table 15.**
Computed values of E_{CG-B} and TE_{CG-B} of the CG-B using the MSAF-17-MULTIEXPANDED-FILTER-14 method and the NN classifier.

**Type of Acoustic Signal** | **E**_{CG-B} (%) |

Healthy CG-B | 100 |

CG-B with a light damaged rear sliding bearing | 100 |

Motor off | 100 |

| **TE**_{CG-B} (%) |

Total efficiency of recognition of the CG-B | 100 |

**Table 16.**
Computed values of E_{CG-B} and TE_{CG-B} of the CG-B using the RMS and the NN classifier.

**Table 16.**
Computed values of E_{CG-B} and TE_{CG-B} of the CG-B using the RMS and the NN classifier.

**Type of Acoustic Signal** | **E**_{CG-B} (%) |

Healthy CG-B | 100 |

CG-B with a light damaged rear sliding bearing | 100 |

Motor off | 100 |

| **TE**_{CG-B} (%) |

Total efficiency of recognition of the CG-B | 100 |