Aircraft Acoustics 101, A Quick Overview
We love airplanes. Big, small, slow or fast, they all have something about them that makes them special. Yet it would be a rare owner indeed that didn't want to have a quiet airplane. Is it even possible? How can it be done?
Given the weight restrictions we ordinarily need to place on an airplane, it is pretty hard to make your aircraft as quiet as a Lincoln Town Car limousine but there are a lot of options that can make it much more pleasant to be in. This section discusses some of the options available and what trade-offs need to be considered using plain English. For a more technical overview, see "At a Glance, Making an Aircraft Quieter".
- I have the very best ANR headset there is, why do I need to add acoustic treatments to my aircraft?
- That is a great question and one that I hear a lot. For many people, that solution is perfectly fine but for others, the ability to talk inside their pride and joy and be heard is a requirement. Or for the long distance flier, maybe the background noise that is not blocked by ANR becomes a nuisance. Perhaps what you really need is mostly thermal insulation and do not need a lot of acoustic treatment. Each pilot will have their own needs and not everyone will place the same emphasis on noise and thermal insulation as others would.
- There are many products out there, which one should I use?
- All of the acoustic treatment products out there will have some effect, the question becomes which one will work best and fits your needs. Generally, a systematic approach is best so some understanding of the technical aspects may be needed... [more]
- Why the emphasis on vibration?
- The largest single contributor to noise in an aircraft is vibration and the majority of that is from the engine (although exhaust and aerodynamic noise are contributing factors). So most of the noise we hear started out as vibration that was carried along the rigid structure of the aircraft before being converted into audible sound... [more]
- How do I eliminate vibration?
- From a practical standpoint, you cannot eliminate all vibration within acceptable weight limits but you can do a lot to mitigate it. The first step is... [more]
- What about damping?
- The concept is to reduce the total amount of vibration just like turning down the volume on a radio reduces the movement of a speaker (but not the frequency). We first tried to keep the vibration from entering the structure with isolation mounting but... [more]
- Is that it for passive vibration control? What's next?
- Yes, that is the basics of VIBRATION CONTROL. From here on, we will be treating NOISE directly... [more]
- So what about absorbers?
- Absorbers are not as effective as barriers in stopping noise from getting inside a plane but they have one tremendous benefit in that they do not need to weigh much to do their job... [more]
- Is that all there is?
- Well, yes and no. The above lists all of the treatments but HOW they are used has a tremendous effect. There are specific strategies that can enhance the benefits of these materials... [more]
