Acoustics, Ergonomics, and Safety Are Paramount

Whether specifying a surface for a sports, fitness or recreation application, there are three essential benefits that all performance surfaces should provide: safety, ergonomics, and acoustics.

Acoustic Considerations

The acoustic issues found in typical athletic facilities stem from the nature of a building’s construction and the specified materials or surfaces. Many facilities feature large, open spaces dominated by hard walls and ceilings that reflect sound. Due to the expansiveness of these spaces, many facilities cannot afford to install new flooring everywhere, so concrete is ever present. This combined with the reflective materials, such as concrete, metal, brick, and plasterboard, used on parallel walls and ceilings makes these spaces very loud.

As such, it is important to isolate or dampen sound as much as possible throughout an athletic, fitness, or recreation facility. Types of sounds to consider isolating include:

• Weights dropping or hitting each other;
• Cardio machines;
• Footsteps or pounding;
• Exercise class music; and
• Structural sounds (HVAC systems, pipes, motors, generators, etc.).

Many of these sounds can travel quickly and create unwanted noise in other spaces within a building by sending vibrations through pipes, frames, ductwork, ceilings, or electrical junctions. To isolate the sounds within an enclosed space and dampen their impact, absorptive materials must be used to shorten or eliminate reverberation, while irregular surfaces should be arranged to reflect sound in different directions.

Impact sound: The energy of a falling object depends on its mass and how far it falls. The falling objects could be footfall on a treadmill, someone jumping off a box, or a dropped dumbbell. Engineered flooring products are designed to manage this energy. The best products to use, and the ways they are tested, depend upon the amount of energy being released and how it should be managed. The energy created from the impact has two general transmission paths, which are:

1. In-room impact noise: The sound level in the room where the impact occurs.
2. Transmitted impact noise: The sound level in the adjacent room.

Transmitted impact noise: Transmitted impact noise is typically measured in the room below where the impact occurs. The tests most commonly referred to for impact noise are the impact insulation class (IIC) and the delta impact insulation class (∆IIC). These tests only address the impact sound transmission to the room below the impact. In addition, the tests are designed to address footfall noise and include the entire floor/ceiling structure, not just the flooring or underlayment.

Acoustics ratings are also important for choosing flooring. However, the specifier should understand the difference between residential and fitness needs.

IIC ratings are a helpful reference for residences and other uses where footsteps are the primary concern for impact sound, but IIC ratings do not apply to noise from heavy weight impacts in gyms. The tapping machine used in IIC and ∆IIC tests has 1.1-pound weights dropped from 1.6 inches. These impacts are not enough to represent the energy from 35-pound dumbbells and kettlebells dropped from 1–2 feet, or 250-pound barbells dropped from 5–6 feet.

A true performance surface provides safety, ergonomic, and acoustic benefits to the people using the surface.

Acoustic Terms and Standards

Impact insulation class (IIC): ASTM E492: Standard Test Method for Laboratory Measurement of Sound Transmission Through Floor-Ceiling Assemblies Using the Tapping Machine measures the reduction of impact noise provided by a floor-ceiling assembly.

Delta IIC (∆IIC): ASTM E2179: Standard Test Method for Laboratory Measurement of the Effectiveness of Floor Coverings in Reducing Impact Sound Transmission Through Concrete Floors measures the improvement from adding the flooring and/or underlayment to a bare concrete slab. It gives a more precise idea of what a product might add to a floor-ceiling assembly.

Sound transmission class (STC): ASTM E90: Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements. Higher values are better as they indicate less transmission of airborne sound. STC is generally not affected significantly by floor coverings and underlayments.

Surface-generated noise: ASTM E3133: Standard Test Method for Laboratory Measurement of Floor Impact Sound Radiation Using the Tapping Machine measures the sound from an impact in the room where the impact occurs. It can be used to evaluate flooring’s ability to reduce noise from footfalls, rolling carts, etc.

Ergonomic Considerations

There are important aspects to consider with regard to both force reduction and energy restitution.

Force reduction and energy restitution: Force reduction is how much energy a surface absorbs. Energy restitution is how much energy a surface returns.

Force reduction adds a level of safety, while energy restitution adds performance and durability. For example, concrete is hard, and it has very low force reduction (-1.9 percent) but high energy restitution (77.2 percent). The result: Concrete returns a lot of energy, which can be tough on an athlete’s joints.

On the opposite end of the spectrum is sand, which has a lot of give. Sand has a very high force reduction (82.7 percent) and low energy restitution (0.5 percent). There is almost no energy being returned here, so it is much more difficult to walk on, since sand is soft and “giving” as you walk.

Every sports, fitness and recreation application requires a performance floor that provides the right balance of energy restitution and force reduction. For example, in applications where heavy weights are being dropped, durability is key, thus requiring a product with higher energy restitution. This type of space demands that a surface is durable enough to withstand the constant drop of weights. For an indoor track, however, some force reduction is necessary to lessen the impact on joints while energy restitution returns energy to keep the athlete going. For applications that are a mix of strength and conditioning or a multipurpose space, an even amount of force reduction and energy restitution is ideal.

Force reduction indicates how much energy a surface absorbs. Energy restitution, on the other hand, indicates how much energy a surface returns.

Safety Considerations

Slip resistance: Slip-resistant flooring should be used in areas that require an extra measure of safety. Vulcanized composition rubber floors are slip resistant whether wet or dry. Embossed surfaces provide slip-retardant performance. Slip resistance can be measured by the coefficient of friction. It is also a good idea to consider colors and patterns that hide the appearance of scuffs, scratches, and abrasion.

Sports Surface Testing Standards

Sports surface testing standards are critical to determine if the surface will perform according to needs specific to sports applications, such as ball bounce, shock absorption, and other factors. The following standard is used to evaluate the performance of sports flooring:

ASTM F2772: Based on Four Criteria

ASTM F2772: Standard Specification for Athletic Performance Properties of Indoor Sports Floor Systems is the testing method for indoor sports flooring.

To meet the ASTM F2772 standard, sports floors are evaluated on four criteria—force reduction (shock absorption), vertical deformation, ball rebound, and coefficient of friction (surface finish effect)—and then classified into one of five performance-level classifications (from Class 1 to Class V). These are the four criteria:

Force reduction (ASTM F2569): The first factor is force reduction, and this portion of the ASTM F2772 standard is tested in accordance with ASTM F2569. A surface’s force reduction is measured as a percentage of how much of the total force of an impact is reduced by the surface on which the object in motion, such as a foot, dumbbell, head, or other part of the body, falls. Per ASTM F2659, a surface’s force reduction may be an “indicator of its performance, safety, comfort, or suitability of the surface.” The more force that a surface reduces, the less chance of injury when an athlete falls on the floor because a percentage of the impact’s shock is being absorbed by the floor.

Vertical deformation (ASTM F2157): Vertical deformation measures the elasticity of a surface under an athlete’s foot or a heavy load. The amount that a surface deflects or “gives” under an athlete’s foot or under a table, chair, or other heavy load can contribute to creating a safer floor that reduces injuries. On the other hand, a surface that gives too much or is too elastic will result in an unstable surface that may contribute to causing injuries.

Ball rebound (ASTM F2117): The way a ball interacts with the playing surface can dramatically affect how a game is played, so it is important that the sports floor does not affect a ball’s ability to bounce. For example, if a basketball game is being played on a synthetic sports floor, the ball should bounce back similarly to how it would on a hardwood basketball court.

The ball rebound portion of the ASTM F2772 test standard is measured in accordance with ASTM F2117. It is calculated by taking the difference in bounce height, when a ball is bounced on the sports floor, compared to concrete. The average of multiple drop points on the floor must meet or exceed 90 percent of the rebound height of a ball dropped on concrete. Any one test point cannot differ by more than 3 percent from the average rebound height. This requirement is to ensure that the sports surface performs uniformly throughout the court.

Surface finish effect (ASTM E303): The surface finish effect portion of the ASTM F2772 test standard measures a surface’s frictional properties. Also known as “slide effect,” this portion of the standard is important to ensure the surface provides the optimal level of traction for an athlete. When athletes are competing, it is important that the floor is not too slippery so that they can change directions and eliminate the worry of falling. However, it is also equally important that the floor does not have too much “grab” because this can increase the risk of injuries.

Athletic flooring with acoustic benefits mitigates impact noise at the source.