Sound Ratings of Industrial Fans
Here’s a fact: Industrial fans cause a lot of sound. Their sounds, which are aerodynamic in origin, are caused by the action of the fan’s propeller or impeller blades, as airflow propagates through the inlet and outlet the exhaust ducts. Other than the airflow, another source of noise comes from the vibration fans running in operation, which is mechanical energy transformed from powering the machine up (electrical energy).
However, these fans, as critical as they are in any production site, are loud machines that will leave your ears ringing in close proximity. This is why it is important to measure how each fan performs, in terms of its acoustics. If not regulated, these large fans can create occupational hazards due to prolonged exposure, especially without the necessary precautions taken.
The OSHA (Occupational Safety and Health Administration) actually requires workplaces to maintain 84 dB (decibels) and below for an 8-hour shift. However, sounds generated by these industrial fans typically register between 70 and 120 dB. And since we’re already speaking in decibels – which is the relative unit measuring sound intensity – let’s talk about sound ratings and their importance in the industrial fan world.
The importance of understanding sound ratings
First, what are sound ratings?
Sound ratings create a quantitative way of identifying the expected sound power that will be emitted by an industrial fan. This measure is able to capture whether noise generated from the heavy machinery is within the acceptable range of human hearing or not. Once identified, this is where noise control measures may need to be applied.
Reducing occupational risks is a priority, but it’s equally as imperative to understand the impact these industrial companies have on the neighbourhoods, establishments, and citizens that are within its vicinity.
So, how can industrial fan sounds be rated? This is done via levels of sound pressure, sound power, or sound intensity.
Identifying sound pressure level
Sound pressure correlates to the amount of sound energy that is able to travel through from a generating source to its receiver. End to end, the air is transmitted into the atmosphere through the inlet. This noise (in the form of atmospheric pressure disturbances) is a by-product of that airflow.
Note, sound pressure levels vary depending on the factors present. How far away are the workstations from the base of the fan? How fast are the fan blades rotating per minute? The measurements of this are very dependent on those various factors and the environment it is situated. Therefore, sound pressure levels cannot be used simply to compare products of the same build quality or type.
Sound pressure can be measured through the use of a sound intensity probe or a microphone. This is usually recorded in Pascals (Pa).
Identifying sound power level
Sound power is the quality of sound that narrows the factor solely to the noise emitted by the source. As it holds all other values constant, the sound power becomes independent from the environment or from the situation where the sound is being made. This is a good measure of the machinery’s specifications and is used primarily when evaluating sound levels.
Most manufacturers are able to calculate for the sound power by identifying and removing noise characteristics attributed to the room or environment.
While the actual value is measured in Watts, it is converted into decibels to keep it within the range for comparison. Sound power will always measure higher than sound pressure levels as the sound power levels are derived from the actual energy produced from the industrial fans.
Measuring sound intensity (dB/Decibels)
Sound intensity is directly correlated to the surface area the sound is able to travel across. Simply put, it’s the sound energy per unit of space. Noise, as it generates away from its source, is able to dissipate as explained by the inverse square law – the reduction of a sound energy over distance.
Is the industrial fan located in an enclosed space? If so, soundwaves are able to reverberate longer, bouncing wall to wall as against it had been in a free field.
Sound intensity uses the unit of measurement watts/m3 ; a vector quantity, dependent on magnitude and directionality of the sound.
How to use sound ratings
Now that you know how industrial fan sounds are rated, understanding how these heavy machineries measure up helps make for better planning and prevention.
1. Planning & Prevention
If you’re deciding between various models, one of the main considerations to start with is to determine where the equipment will be installed. This is so that the industrial fans are located away from sensitive receivers (such as residential buildings or schools) or inside the plant layout, where it’s situated within safe distance from the workers.
Another point would be the selection of high-quality equipment. With more and more technologies coming out that are able to dampen these noises, there are various noise control techniques to choose from. These problems may be lessened in the selection of quieter industrial fans (with built-in silencers and damping compounds) or selecting systems with the right casings and build.
2. Practical Remedies
Relocation of the equipment is an immediate alternative. Given the restrictive space where sound reverberates, free fields or open spaces will allow for sound waves to dissipate quicker.
Another way to help reduce exceeded sound ratings is the reduction of fan speeds, particularly when the production is not expected to operate at full capacity. Larger fans that operate at lower RPMs are able to produce a much quieter sound.
If all other means have been exhausted and there is no another way to reduce sound pressure levels, ensure that measures are made to reduce the impact of exposure with the aid of hearing protectors.
Ear plugs with NRR (Noise Reduction Rating) will help aid in the protection, should the noise levels go beyond 84 dB. Especially for workers in major industrial sites, duration is equally important to the intensity of these sound levels, particularly when dealing with them day in and day out. Ideally, this should be the last resort in terms of a hierarchy of control, as it is less effective compared to eliminating the issue at the root source.
Ultimately, industrial fan sounds are quantified by manufacturers as sound power and must be used in correlation to the environment, directionality, and spatial, as well as environmental factors to gauge closer to the expected sound level.
Ferrari Ventilation has been manufacturing top quality industrial fans since 1963.