Rail Vehicles and Acoustic Insulation: Improving Passenger Comfort and Safety

Acoustic insulation for rail vehicles

Rail Vehicles and Acoustic Insulation: Improving Passenger Comfort and Safety

While many people rely on cars for transportation, trains and trams remain popular for cost-effective mass transit. Nowadays, mass transportation designs primarily focus on passengers’ safety and comfort. However, the level of heat and noise generated by rail vehicles, such as trains, can make them quite uncomfortable for passengers when unmitigated. Thankfully, there are several sound and thermal insulation options that can reduce, block, or absorb vibrational noise and heat. This article discusses noise management in rail vehicles through the use of acoustic insulation to better ensure passenger comfort and safety.

Why Is Acoustic Insulation Important in Mass Transportation?

When people hear of pollution from mass transportation, they only think of soot and fumes that cause air pollution. Nonetheless, trains and other rail vehicles also expose passengers and operators to noise pollution from the forces of movements and moving parts like engines.

Continuous exposure to this noise, as happens for operators working for extended periods, and repeated exposure for passengers using mass transportation can result in stress, disorientation, and hearing damage.

Growing research on the effects of noise pollution has also associated it with sleep issues, an increased risk of cardiovascular disease, cognitive impairment in children, and elevated hormone levels. Acoustic insulation of rail vehicles is the best way to protect passengers and workers from health-damaging noise. For this reason alone, rail vehicle manufacturers must continue to improve noise management in their vehicles. Insulating rail vehicles with soundproofing materials not only protect passengers and workers from noise but is also a key selling point for manufacturers, increasing profits while improving the comfort and safety of their vehicles.

Causes of Noise in Rail Vehicles

Noise in rail vehicles comes from both internal and external sources.

  • Internal sources include noise and vibration noise caused by engines and large structures such as floors, roofs and doors. Other sources of noise include friction between wheels and rails and vibration of ventilation ducts.
  • External noise sources experienced by rail vehicles are primarily due to vehicle speed and air turbulence. Both can cause structures such as roofs and wall panels to vibrate heavily. Proper sound insulation can help mitigate these problems. Other sources of external noise include traffic encountered (on or around the tracks), high winds, and rain.

Where Is Acoustic Insulation Required?

Regulations and standards play a key role in the design and manufacture of rail vehicles, with each country and government having its own rules. Noise levels have been set not only for the external noise generated by the vehicle but also for the internal noise. In order to meet these internal noise level standards, train and tram manufacturers need to better address noise issues. Three solutions are currently used in the transportation industry:

1. Sound absorbing to absorb sound waves in the vehicle
2. Sound deadening to stop vibrations and rattles
3. Sound blocking to prevent external noise

Below are the main areas in rail vehicles that require acoustic insulation.

Engine Insulation

When soundproofing rail vehicles’ engine rooms, sound insulation panels with membrane absorbers are the best choice. These panels have a special foil on their surfaces to keep the soundproofing material from getting contaminated by oil and splashes. Self-adhesive sound insulation panels are also an option.

As for the engine itself, customized molded foams and damping pads can help prevent excess noise, heat and vibration at the source.

Walls and Ceiling Insulation

Metal vibrations and external noise can travel through rail vehicle walls and ceilings, making the environment very uncomfortable. To cut out unwanted noise, sound-absorbing materials such as acoustic foams can be installed on the side walls and ceiling

Melamine foam is typically the preferred acoustic foam used for wall and ceiling insulation. Melamine foam is a lightweight material that shows exceptional resistance to heat, low flame propagation, and smoke.

Floor Insulation

A significant portion of noise in rail vehicles comes through the floor or undercarriage. This is because it is not very thick and is close to the ground.

Noise control for the vehicle floor entails placing noise-dampening mats, also called foam shields. The mats are made of thick, durable material that absorbs noise while reducing resonance.

Air Ducts

Transit vehicle air ducts can also be insulated to reduce noise levels from filtered air in passenger cars and locomotive interiors. This acoustic and vibration insulation also improves the efficiency of air conditioners and helps maintain low temperatures.

Things Considered When Selecting Acoustic Foams

When it comes to selecting acoustic foams for rail vehicles such as trains and trams, there are several things to consider. Below are the three most important ones.


An important element of acoustic foam selection is the type of compound used. Silicone foam composites and silicone foams with acoustic insulation have outstanding temperature resistance, making them ideal for use in high-temperature environments. Acoustical-grade urethane foam composites, n the other hand, have excellent heat, chemical, and moisture resistance. Lastly, acoustic melamine foams are extremely lightweight and resistant to low flame propagation, heat, and smoke.

Sound Frequencies Blocking

Another critical factor to consider is the foam’s ability to block specific sound frequencies. Acoustic insulation is designed to block a specified range of frequencies and is classified by specific sound transmission classes (STC), noise reduction coefficients (NRC), and sound reduction indices (SRI). It’s important to keep these frequencies in mind when choosing the right foam for rail vehicles.


Acoustic insulation foams vary by applications and industries that should use them. For instance, in passenger rail cars, the foams should meet specific FST (flame, smoke, and toxicity) standards like Bombardier 800-C or ASTM E84. Melamine acoustic foam, for example, is made of a synthetic compound and is resistant to chemicals and fire. It has excellent soundproofing and thermal insulation abilities, effectively reducing noise in vehicles that travel on rails. Moreover, it is fireproof and thus increases your rail vehicle’s safety.

In Conclusion

Acoustic insulation is an essential element in the design of rail vehicles that improves passenger safety and comfort while reducing the risk of health problems related to noise pollution. Acoustic foams and acoustic barriers can reduce internal and external noise sources by attenuating, blocking or absorbing sound waves. Engine compartments, walls, floors, ceilings and ventilation ducts are all areas requiring sound insulation in rail vehicles. In addition to the area to be insulated, the selection of the appropriate acoustical foam will be based on the compound from which the foam is made and the sound frequencies to be blocked. Quieter vehicles not only protect passengers and workers from noise but can also serve as a selling point to increase profitability.

The ID Group offers a variety of solutions to OEM manufacturers of mass transit vehicles, such as trains and trams. Our noise and heat management solutions include acoustic foam panels, acoustic barriers, thermal foams, molded foams, and dampening pads. We also offer custom cutting services to meet your unique application. Let us know your challenges, and we’ll help you find a solution.