Technicians understand the shop is a noisy place, especially when tools and air compressors are running in full force. Pneumatic tools are one of many sources of noise found in a workshop. To help reduce some of that noise, Ingersoll Rand engineers their products to have low noise and vibration levels to create a more ergonomically correct experience for the tool users.
In order to better understand how Ingersoll Rand engineers products to reduce noise, it’s important to understand where the noise comes from. In a pneumatic tool, noise is created in three ways:
1.) Process noise — the noise that is generated from the tool in contact with the work piece
2.) Exhaust noise — the noise that is generated by the air exiting the tool
3.) Vibration-radiated noise — the noise that is generated from gears and bearings
Process noise ultimately becomes the responsibility of the user to reduce. Ways to reduce process noise include better clamping of the part noise treatment surrounding the work piece, covering the impacting hammer with a heavy rubber jacket, maintaining sharp tools and wearing hearing protection.
Exhaust noise is often identified as the primary noise source. Most rotary pneumatic tools are driven by sliding vane motors. The action of the air turning the rotary vane motor is the primary cause for the exhaust noise. To overcome the problems of exhaust noise, pneumatic tools often have a muffler that is located inside the tool. There are many challenges in designing pneumatic tool mufflers. For example, the muffler must be very compact in size, have an extremely low pressure drop, and be capable of lessening noise over a wide range of frequencies. Furthermore, it is necessary that the part have an infinite life. The muffler should never fail or cause the air passages to become blocked by obstructions. Ingersoll Rand has patented designs to reduce the noise without penalizing the performance of the tool.
The third source of noise is noise radiated from the tool-housing vibration. The main contributor to vibration noise is the physical dynamic motion of the mechanical components inside the tool. To reduce vibration noise, special care is taken by the engineers at Ingersoll Rand to design parts that are precisely balanced and the motion of these parts is designed to minimize the amount of vibration through the use of counterweights and other engineering techniques.
“Often a piece of machinery has more than one source of noise. To reduce the noise, the engineer must know the loudness of each noise source, and then reduce the noise beginning with the loudest source,” says Mike Lucas, principal engineer, Air Solutions at Ingersoll Rand. “Our goal as a design team is to develop products that are the quietest in the marketplace. Our engineering teams are dedicated to achieve this very important goal.”
Ingersoll Rand’s engineers follow standard practices and procedures for measuring and quantifying the noise level of a pneumatic tool. It is industry practice to follow ISO 15744 – Hand-held non-electric power tools – Noise measurement code – Engineering method (grade 2). Contained in this standard is a description of the measurement procedure.
In accordance with ISO standards, Ingersoll Rand tests each pneumatic tool using five microphones positioned on four sides 1 meter from the geometric center of the tool and one meter above the tool. The photograph illustrates a typical setup.
Today, Ingersoll Rand measures the noise level of all its tools in an anechoic testing room to determine the sound power level in A-weighted decibels. An Ingersoll Rand pneumatic drill with Quiet Tool technology is approximately 80dB decibels, which is comparable to a garbage disposal at three feet.
Why is the noise level of a tool important? Hearing loss is a public health problem, and will continue to become more prevalent. Lucas notes that in many cases, hearing loss is related to age and occupation, so it’s possible that the noise you’re exposed to now may affect you more significantly later in life. It’s extremely important to not only avoid excessively high noises in general, but also to wear the appropriate hearing protection whenever possible. Public health officials consider our ears our “first line of defense” in the workplace — if your job requires you to have conversations or hear sounds (such as alarms), diminished hearing can be a hazard.
For more information about Ingersoll Rand tools, visit ingersollrandproducts.com.