Soundproof Fabric Testing

Sound insulation cloth testing mainly conducts scientific testing and analysis on key performance indicators, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Sound Insulation Cloth Testing Items

Sound transmission loss (STC/OITC): The sound transmission loss is the core indicator for evaluating the airborne sound insulation performance of the sound insulation cloth, usually using the Sound Transmission Class (STC) to evaluate medium and high frequency human voices and the Outdoor-Indoor Transmission Class (OITC) to evaluate medium and low frequency traffic noise. The test is carried out in a standard reverberation room and anechoic room, and is obtained by calculating the logarithmic difference between the incident sound energy and the transmitted sound energy.

Sound absorption coefficient (NRC): The sound absorption coefficient reflects the ability of the material to absorb the incident sound energy, with the Noise Reduction Coefficient (NRC) used as the single-value evaluation indicator. The standing wave tube method or the reverberation room method is adopted for testing, measuring the sound absorption performance of the material in the six frequency bands of 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz and 4 kHz, and the NRC is the arithmetic mean of the sound absorption coefficients of the latter four frequency bands.

Surface density and thickness: The surface density refers to the mass of the material per unit area (kg/m²), and the thickness refers to the vertical dimension of the material under a standard pressure (mm). These two basic physical parameters directly affect the mass law of sound insulation of the material, and are important bases for calculating the theoretical sound insulation value and judging the uniformity of the product. An electronic balance and a thickness gauge are needed for multi-point measurement and taking the average value.

Tensile breaking strength and elongation: This test evaluates the mechanical durability of the sound insulation cloth during installation and use. In accordance with the fabric tensile test standards, a universal material testing machine is used to apply a longitudinal tensile force to the sample, recording the maximum force and elongation percentage at breakage, ensuring that the material can withstand construction tension and structural deformation without damage.

Flame retardancy: For application scenarios with fire protection requirements such as building and vehicle interiors, flame retardancy tests need to be carried out in accordance with the relevant standards (such as GB 8624 and FMVSS 302). The burning rate, afterflame time, afterglow time and melt dripping of the sample are mainly examined, to rate its burning grade and ensure use safety.

Environmental protection and hazardous substance release: Tests whether the sound insulation cloth contains or releases hazardous substances, such as formaldehyde, TVOC (total volatile organic compounds), heavy metals and polycyclic aromatic hydrocarbons (PAHs). Sampling and analysis are carried out in accordance with the relevant environmental protection standards (such as GB 18587, REACH and RoHS), ensuring that the product meets the indoor environmental health requirements.

Sound Insulation Cloth Testing Scope

Sound insulation cloth for buildings and decoration: Mainly applied in walls, ceilings, pipe wrapping and floating floor interlayers of buildings such as residences, hotels and offices, to isolate airborne sound and impact sound. Testing needs to focus on its sound insulation and absorption performance in the medium and low frequency (living noise) and medium and high frequency (human voice and TV sound) bands.

Sound insulation cloth for vehicle interiors: Applied to the ceilings, door panels, carpet bottoms and engine compartment sound insulation covers of automobiles, high-speed trains, aircraft and other vehicles. In addition to the acoustic performance, the testing scope needs to be extended to harsh environmental adaptability indicators such as resistance to high and low temperatures, oil stains, aging, flame retardancy and low VOC release.

Sound insulation cloth for industrial equipment and pipe wrapping: Used for sound insulation wrapping of noise sources such as factory fans, pumps and air conditioning units, as well as ventilation ducts. Testing needs to focus on evaluating the sound insulation effect of the material under high sound pressure levels and broadband noise, as well as its long-term stability such as corrosion resistance, moisture resistance and mold resistance.

Specialized acoustic cloth for recording studios and audio-visual rooms: This type of sound insulation cloth usually has good acoustic tuning functions (absorption or diffusion at specific frequencies) and sound transparency (used in front of speakers). The testing scope includes the precise acoustic spectrum curve, sound transmission loss, appearance texture and fire rating.

Damping layer/constraint layer in composite sound insulation materials: The sound insulation cloth is often used as the constraint layer of the damping coating or combined with other materials (such as foam, rubber and steel plates) into a sandwich structure. During testing, the composite body needs to be evaluated as a whole, evaluating its sound transmission loss, damping loss factor and vibration transmission loss.

Sound insulation cloth with special functions: Including sound insulation products with additional functions such as electromagnetic shielding, waterproof and breathable, self-cleaning and antibacterial and anti-mold. The testing scope needs to cover the effectiveness verification of its special functions, ensuring that the additional functions do not affect the core acoustic performance.

Sound Insulation Cloth Testing Methods

Reverberation room-anechoic room method (sound transmission loss test): This is the laboratory standard method, in accordance with the ISO 10140 or GB/T 19889 standard series. The sound insulation cloth sample is installed on a standard test window, placed between the adjacent reverberation room (source room) and anechoic room (receiving room), and the sound transmission loss at one-third octave band center frequencies from 100 Hz to 5000 Hz is measured, and then the single-value evaluation quantity is calculated.

Standing wave tube method (sound absorption coefficient test): Suitable for testing the normal incidence sound absorption coefficient of porous sound insulation cloth, in accordance with the ISO 10534 or GB/T 18696 standards. The sample is placed at one end of the standing wave tube, and by moving the probe tube to measure the maximum and minimum values of the standing wave sound pressure formed in the tube, the sound absorption coefficient at each frequency is calculated. This method requires a small sample, but only reflects the normal incidence characteristics.

Reverberation room method (sound absorption coefficient test): Used to measure the sound absorption performance of the material under a diffuse incident sound field, in accordance with the ISO 354 or GB/T 20247 standards. A large-size sample is placed in the reverberation room, and by comparing the change of the reverberation time before and after placing the sample in the empty room, the sound absorption coefficient from the 100 Hz to 5000 Hz frequency band is calculated. The results are closer to the actual application scenarios.

Impedance tube transfer function method: This is a more advanced sound absorption and sound insulation test method, in accordance with ISO 10534-2 (sound absorption) and ISO 15186 (sound insulation). Using two or four microphones, by measuring the transfer function of the incident signal and the reflected signal (sound absorption) or the sound pressure on both sides (sound insulation), the acoustic parameters of the material are quickly and precisely obtained, suitable for R&D and quality control.

In-plane tensile test method: In accordance with fabric tensile test standards such as GB/T 3923.1 or ISO 13934-1. Strip specimens of a specified size are cut, clamped in the upper and lower grips of a tensile testing machine, and stretched at a constant rate until breakage. The system automatically records the force-displacement curve and calculates the breaking strength and elongation at break.

Cone calorimeter method (combustion performance): This is an advanced method for evaluating the combustion behavior of materials. Under standard heat radiation conditions, the sample is ignited, and key fire parameters such as the heat release rate, total heat release, smoke production and CO generation are precisely measured, which can more scientifically evaluate the real fire hazard of the material.

Testing Instruments and Equipment

Acoustic reverberation room and anechoic room system: This is the core facility for standard sound insulation and sound absorption testing. The reverberation room requires that the sound field in the room is fully diffuse, and the anechoic room requires an extremely low background noise and fully sound-absorbing boundaries. The system includes a standard sound source (omnidirectional loudspeaker), high-precision microphone array, data acquisition and analysis system and a standard test window/specimen holder.

Impedance tube and microphone set: Used for the transfer function method testing. The equipment includes rigid circular tubes of different diameters (covering different frequency ranges), two or four high-precision phase-matched microphones, preamplifiers, power amplifiers and loudspeaker sound sources. The supporting analysis software can calculate the sound absorption coefficient, acoustic impedance and sound transmission loss according to the transfer function.

Universal material testing machine: Used for mechanical property testing. The equipment should have high-precision force sensors and displacement sensors, and the grips need to be suitable for soft materials such as fabrics, preventing slipping or clamping damage. The computer control system can set the tensile speed and collect and process the force and deformation data in real time.

Flame retardancy test chamber: Configured according to the specific standards, such as horizontal and vertical burning test chambers, oxygen index meters or cone calorimeters. The combustion chamber needs to be equipped with a standard igniter, specimen holder, scale and automatic timing device. The cone calorimeter integrates complex modules such as a heat radiation source, electronic igniter, gas analyzer and smoke density meter.

Chemical analysis equipment such as gas chromatography-mass spectrometry (GC-MS): Used for environmental hazardous substance testing. GC-MS is used to analyze organic volatiles such as VOCs and formaldehyde; atomic absorption spectrometers or inductively coupled plasma mass spectrometers are used to detect heavy metal content. In the sampling link, sample pretreatment equipment such as climate chambers or thermal desorption instruments also need to be equipped.

Basic physical parameter measuring tools: Including high-precision electronic balances (for measuring the surface density), digital thickness gauges (with a standard pressure foot and weight, for measuring the thickness), and tape measures or image dimension measuring instruments (for measuring the sample size). Although these tools are simple, their precision is directly related to the accuracy of the subsequent acoustic and mechanical test data.

Testing Standards

Domestic Standards:

1. GB 8624, Classification for burning behaviour of building materials and products

2. GB 18587, Indoor decorating and refurbishing materials — Limit of harmful substances of carpets, carpet pads and carpet adhesives

3. GB/T 3923.1-2013, Textiles — Tensile properties of fabrics — Part 1: Determination of breaking force and elongation at breaking force using the strip method

4. GB 18401-2010, National general safety technical code for textile products

International Standards:

1. ISO 13934-1, Textiles — Tensile properties of fabrics — Part 1: Determination of maximum force and elongation at maximum force using the strip method

2. ISO 105, Textiles — Tests for colour fastness

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.