How Vibrations Affect Both Structures and Humans
Vibrations are an interesting mechanical phenomenon that can cause pleasure or pain, depending on the specifics of the vibration. A night spent at the symphony and an afternoon spent at work while a jackhammer demolishes the sidewalk outside your window are both experiences driven by vibrations. One is a relaxing retreat from your busy work week, while the other may drive you nuts and negatively impact your productivity.
The vibration effects on structures and humans have been studied fairly extensively, and we know much more now than we did just a couple of decades ago. Understanding vibrations and their effects on anything with mass will underscore how important noise and vibration control are in our world.
What are vibrations?
Vibrations are all around us. Nearly every motion creates some type of vibrations, whether we recognize them or not. But what are vibrations? Vibrations are oscillations that occur about an equilibrium point. Simple, right?
If you’ve ever watched someone jump on a trampoline, you’ve got a great visual reference to get you started understanding vibrations. The jumping surface is taught at rest, which is its equilibrium point. When someone jumps up and down, the trampoline vibrates. The surface moves up and down, eventually returning to its equilibrium. It’s very similar to what you see when someone plucks the strings of a musical instrument.
As the energy waves are transferred to the air and structures around the source of the vibrations, those energy waves can create sounds, and the vibrations can transfer through other structures and bodies.
Vibration effects on structures
Many everyday vibrations have little or no effect on structures, but some can cause the structure to weaken or even fail entirely. Throughout history, we’ve built structures that stood the test of time, and we’ve built structures that unexpectedly came down in remarkable fashion. We’ve learned a bit about resonance in studying the doomed structures and what caused them to collapse.
Resonance occurs when the frequency of a vibration matches and forces the structure to vibrate at its natural frequency. The natural frequency is the frequency of the material when not exposed to outside drivers or vibration dampers. A vibration damping material is anything that provides resistance to the oscillations and causes the vibrating material to return to its equilibrium point.
The natural frequency of any object is defined by its mass and rigidity. The easiest way to demonstrate natural frequency is by using tuning forks as an example. The specific design of each tuning fork is such that the natural frequency corresponds with the note it’s tuned to. Changing the mass or rigidity of the tuning fork will change its natural frequency, and therefore the note produced by the fork.
Prolonged exposure to damaging vibrations can cause nails to move, bolts to loosen, and the foundation to crack. In other words, nothing good. When vibrations occur in structures, whether they’re produced by traffic, construction, music, or simply foot traffic in the building’s hallways, they can have an effect on the building’s structural integrity. They can also have an impact on the humans living and working inside.
Vibration effects on humans
Most of us find the effects of sound vibration on the human body to be pleasant in nature. Our stress levels decrease, and we feel the urge to tap our toes and nod our heads. In fact, there is a body of evidence that suggests music therapy can be incredibly beneficial in treating several spiritual and physical ailments. As great a prospect as music therapy is, not all vibrations are helping and healing. Some vibrations can have detrimental effects on our bodies and minds.
People exposed to high levels of vibrations on a regular basis can experience adverse physical effects of vibration on the human body.
- Those who regularly use electrical hand tools like grinders and drills can damage nerves and muscles, leading to chronic numbness and tingling.
- When we’re exposed to whole body vibrations due to standing on or riding in vibrating machinery, we can experience a whole host of additional symptoms, including chronic back pain, motion sickness, and sleep disturbances.
- Many vibrations arrive with the presence of very loud sounds, which can cause us to experience issues related to hearing loss or tinnitus, which is a persistent ringing in the ears when no sound is present. The extent of the damage can vary based upon the volume of the noise and the frequency of exposure.
The effects aren’t just physical. Chronic exposure to vibrations and sounds can lead to emotional distress as well. When we’re exposed to high levels of noise pollution, we are prone to becoming more irritable, tired, and frustrated. The sound itself can exacerbate these problems. Think about how you feel when someone scratches a chalkboard – if you’re old enough to remember chalkboards – or endlessly clicks a retractable pen.
With all the potential effects that go along with abundant vibrations, it’s important to tackle them in the design phase of the structures we spend our lives in.
Now that we are familiar with some of the vibration effects on both structures and the human body, it’s time to do something about them. Utilizing noise and vibration control products in the construction of our buildings and vehicles is an important part of keeping them safe and keeping their occupants safe.
There are three main sources of vibrations that we have to contend with.
Sounds that emanate from the world around us are considered environmental sources. This includes things like construction noises and the sounds of local traffic passing your building. Before you ask how to reduce traffic vibrations, I’ll save you the trouble. You probably can’t. What you can do is reduce the effect of those traffic vibrations on your building and its occupants.
With enough road vibration, damage to buildings can occur. That’s why structural engineers address the ground vibrations in the foundation or slab itself. While there’s little you can do yourself on that front, you can do some things to keep vibrations from causing harm to your existing structure, as well as the health of the people inside.
Vibrations don’t only transfer through the ground. They also pass through the air and into the exterior walls and windows. The windows are going to be the easiest point of passage from the outside to the inside. If you’ve got aging windows, you may need to bring them up to date. Window inserts can keep noise from passing through the windows without replacing an entire wall of windows. Hang acoustic curtains in front of the windows, and you’ve got a double defense against vibrations.
Even when the offices are empty, and the streets are silent, most buildings are still humming with vibrations. The pumps and pipes and all the equipment that keeps a building running cause vibrations and sounds. When combined with environmental sources and human activity, they can be a significant contributor to noise pollution. With this type of vibration, you want to stop it at the source. Vibration isolators are going to be your go-to option. So, how do vibration isolators work?
When things like HVAC components and water pipes operate, they transfer vibrations directly to the surface they’re resting on or mounted to. Vibration isolators stop the transfer of those waves by providing a buffer between the utility and the surfaces of the structure in which it lives.
For example, if you want to reduce pipe vibrations, wrapping them in a noise barrier can keep the vibrations from transferring into the hangers or clamps and into the structure itself. You can also quiet noisy laundry machines by placing them on vibration isolating pads. No matter where vibrating equipment causes noise and movement, there are vibration isolators that can help.
When we walk through our environments, we create ground vibrations. We may not always notice them, but our downstairs neighbors could have a word or two to say on the subject. If you watch late night blockbusters in a room adjacent to the one your early-rising spouse sleeps in, they might implore you to learn how to reduce subwoofer vibration through walls. The point is that vibrations travel through our interior walls and floors, so it’s important that we acoustically treat them.
Duracoustic S.T.O.P. floor underlayment is an excellent option in the case of vibrations caused by foot traffic. Rolling a layer out between layers of flooring can prevent the passage of considerable amounts of vibration from one side to the other. This means that your late night snack run won’t wake the downstairs neighbors.
If sound passage between rooms on the same floor is your main issue, adding mass-loaded vinyl to your walls can help minimize it. It creates an environment where binging your shows won’t wake your family in the next room. You can also reduce sound and vibration transmission by absorbing more of them before they reach the walls with things like softer furniture and acoustical wall panels.
Getting a plan in place
We all know that unwanted vibrations can cause our stress levels to rise, but not many of us know how to do anything about it. As you get started on your journey, learning more about the characteristics of structural vibrations will help you devise your plan. Take some vibration measurements if you need to, and identify the products that will help minimize the vibration effects that are causing you pain.