How do elbows compare to sound attenuators?

There are many issues revolving around industrial noise. In order to avoid them, you need to use specialist equipment. For years, we have been supplying solutions in the form of high calibre attenuator models. Also known as a silencer, they will minimise the noise at a variety of facilities.

One common belief is that placing several elbows close to an air handling unit (AHU) can produce the same insertion loss as a duct attenuator. Elbows might be less expensive than attenuators. However, we need to think about the acoustical performance of using a low cost substitute.

Let’s examine the two designs. Utilising the tables provided in the 2007 ASHRE handbook – HVAC applications, for each kind of elbow, the width has to match or surpass 30 inches. This is so it can achieve any kind of insertion loss at 63 Hz. With a 30-inch-wide elbow, it will only supply 1dB of insertion loss at 125 Hz. When lowering sound from AHUs, these two frequencies are normally of concern.


At 63 Hz, elbows need to be 60 inches wide at least to get into the IL domain of sound attenuators at 4dB. The width dimension here is 30 inches for 125 Hz at minimum.

As for an attenuator, they tend to have around 4 to 10dB of IL at 63 Hz, as well as 8 to 20dB at 125 Hz. Certain designs will offer users much bigger IL than this.

It is not hard to see that for smaller elbows, IL equivalence between attenuators and elbows is tricky or outright impossible to achieve. At the bigger duct sizes, you would have to carefully design the system to acquire equivalent low frequency IL.

With the higher frequencies, attenuators normally offer 20 to 40dB of IL. This is in the mid frequency bands, as well as 10 to 15 at the highest tested frequencies. If this is where you demand IL, the sound attenuator will be the far superior option.

Talk to us to design a quality attenuator

At Ventx, we can provide you with the perfect silencer designs. With the help of our acoustic modelling software, we will create a solution that meshes perfectly with your current systems. It will provide the perfect marriage of noise reduction and long term value.

So, if you want to work with us, feel free to get in touch.