**3.11. Measurement of sound insulation**

An unwanted noise, a part of sound is irritating and which caused many problem of human related to mental and psychological aspects. Jute needle-punched nonwoven textile materials have good property to control sound if they are properly designed for this purpose. A simple design of such an instrument to measure the sound insulation of the textile nonwoven materials has been explained by Sengupta, 2010 [22]. It consists of a sound insulating box which is made out of 12 mm thick rigid plastic (acrylic sheet) and has a provision of removable top lid. Inside one vertical wall of this box, a sound source and a decibel meter (s) are fixed. In another movable (to adjust the distance between sound source and receiver) vertical wall, a decibel meter (R) is fixed coaxially opposite to the sound generator to measure the sound intensity. In between these two decibel meters, a sliding (to adjust the distance between sound source and fabric) arrangement is there to fix the fabric sample vertically. An electrical panel has been used to control the sound intensity. Figure 4 shows the schematic diagram of the sound insulation tester as described above [22].

**Figure 4.** Schematic diagram of sound insulator tester [22]

Operating the control panel, a sound of particular decibel sound is created. The source decibel and the receipt decibel are measured by two-decibel metres S and R, respectively, without and with fabric samples. The sound reduction responsible for fabric, where sound insulation is expressed as the difference between the decibel reduction with sample and decibel reduction without sample, is shown below:

$$db\_F = (dB\_S - dB\_R)\_{WS} - (dB\_S - dB\_R)\_{WOS}$$

where dBF is the sound reduction responsible for fabric; dBS is the sound intensity at source; dbR is the sound intensity at receiver; WS is with sample; and WOS is without sample.

#### **3.12. Measurement of electrical resistance**

Textile materials have good electrical insulation property provided they are in dry condition. There are many such applications where the textile materials (fibre/yarn/fabric) are used as electrical insulation purposed. The electrical insulation application of the textile materials are used in medium voltage ranges (within 415 V). To measure the electrical insulation a circuit is necessary which measures the current-voltage (V-I) characteristics of textile material as shown in Figure 5 [23-24].

Design, Development, Characterization, and Application of Jute-based Needle-Punched Nonwoven http://dx.doi.org/10.5772/61705 289

**Figure 5.** Circuit for electrical resistance of nonwoven [23]

**Figure 6.** Sample holder

another movable (to adjust the distance between sound source and receiver) vertical wall, a decibel meter (R) is fixed coaxially opposite to the sound generator to measure the sound intensity. In between these two decibel meters, a sliding (to adjust the distance between sound source and fabric) arrangement is there to fix the fabric sample vertically. An electrical panel has been used to control the sound intensity. Figure 4 shows the schematic diagram of the

Operating the control panel, a sound of particular decibel sound is created. The source decibel and the receipt decibel are measured by two-decibel metres S and R, respectively, without and with fabric samples. The sound reduction responsible for fabric, where sound insulation is expressed as the difference between the decibel reduction with sample and decibel reduction

=- -- ( )( ) *F S R WS S R WOS db dB dB dB dB*

where dBF is the sound reduction responsible for fabric; dBS is the sound intensity at source; dbR is the sound intensity at receiver; WS is with sample; and WOS is without sample.

Textile materials have good electrical insulation property provided they are in dry condition. There are many such applications where the textile materials (fibre/yarn/fabric) are used as electrical insulation purposed. The electrical insulation application of the textile materials are used in medium voltage ranges (within 415 V). To measure the electrical insulation a circuit is necessary which measures the current-voltage (V-I) characteristics of textile material as shown

sound insulation tester as described above [22].

288 Non-woven Fabrics

**Figure 4.** Schematic diagram of sound insulator tester [22]

**3.12. Measurement of electrical resistance**

in Figure 5 [23-24].

without sample, is shown below:

This circuit consists of sample holder (S), variac (B), rectifier unit (D), ammeter (A), voltmeter (V), and 10 MΩ discrete resistance (R). Two bulldog-clips are used between which the sample is placed (Fig. 6) with gauge lengths 2.54, 5.08, and 10.16 cm. The sample is in series with a known resistance (10 MΩ) and is connected to a D.C. power supply. The voltage is varied from 80V to 220V in 5 steps and corresponding current through the sample is measured after 10s to calculate the resistance [25-26]. The measurement is done at 27ºC and 65% relative humidity. Five sets of voltage-current readings are taken for plotting V-I characteristic curves. The slope (voltage/current) or resistance for each V-I characteristic is determined. The specific resistance has been calculated normalizing the resistance by thickness [multiplying/dividing the resistance (Mega ohm) by thickness (cm).
