Fun Facts: Resonance or if system vibrations build up
When thinking of resonance and race tracks the most obvious link appears to be the roaring of engines. But, it actually covers a much broader scope, which has been exhibited by Renault’s clever engineers at Formula 1.
In 2005 they initially used a so-called tuned mass damper (TMD) for the R25 model. That same year Fernando Alonso achieved his first World Championship title and Renault triumphed as well, winning the Constructors’ Championship. This technology that uses movable weights installed on the front and rear axles to reduce vehicle movements leads to a significant advantage when it comes to uneven grounds or extreme braking manoeuvres.
Due to the fact that this system gave Renault the opportunity to stay ahead of their competitors – since every tenth of a second counts in formula 1 – Pat Symonds, former chief engineer at Renault, really tried to argue for this innovation. But after several other teams including Ferrari and Red Bull, developed similar versions for the following season, the Court of Appeal of the International Automobile Federation (FIA) categorized the mass damper as “movable aerodynamic devices” and consequently, as contrary to the regulations. Their use was forbidden while the 2006 season was still on.
Seasick in a skyscraper – resonance in architecture
Mass damping is also used for other applications, for example, when buildings are affected by vibrations with a constant frequency. Residents of skyscrapers often complain about symptoms similar to the indicators of seasickness whenever buildings are exposed to earthquakes or severe storms. The Japanese have even created a specific term: “Jishinyoi” (the “earthquake-drunkenness”). In order to protect buildings and their occupants, tuned mass dampers have been designed. They consist of huge pendulums that weigh several tons and are installed in the top level of a building to dampen vibrations.
This technology has proven its reliability and is used worldwide for the construction of skyscrapers. So residents of high buildings tend to have a “calmer” life and, in addition, it ensures increased stability and therefore structural security.
Due to this main advantage the tuned mass dampers are used for bridge construction as well. Even though there is no secret about how resonance occurs, numerous examples exist that describe resonance catastrophes of bridges caused by vibrations due to pedestrians or wind storms.
A frog in a tree – resonance in the animal kingdom
You could fill books with examples of resonance. Even animals make use of this phenomenon: Male Bornean tree frogs (Metaphrynella sundana) try to increase their chances to attract females by choosing a water-filled hole in a tree for their mating call.
With different “test tones” the frog approaches the level of the relevant resonance frequency in the specific tree hole. The impressive escalation of the sound by 10 to 15 decibels usually creates the desired effect and the “rhythmic serenade” leads to a first rendezvous.
Vibrational impact on humans and machinery
“Rhythm”, by the way, is just a general term for constant repetitions. Vibrations in comparison are defined by a sinuous movement influenced by amplitude and frequency. Vibrations are an unconscious part of our day-to-day life. Not only do they play a major role in formula 1 but also in general automobile manufacturing. If the effects of vibrations were not considered, drivers would have to deal with so-called travel sickness even more frequently.
When driving, whole-body vibrations (WBV), mainly transmitted by the car seat, have an impact on the human body. Therefore, a seat is best designed in accordance with the chassis and the body of a car to dampen undesired vibrations. Scientific tests have proven that vibrations from 4 to 9 Hz can cause discomfort while higher frequencies could lead to back pain (8 to 12 Hz) or headaches as well as muscle tensions (13 to 20 Hz).
In order to design more convenient car seats, BMW developed a method that combines measured values with subjective perceptions of test drivers. Apart from measurable aspects such as shape, material and dynamic behavior of the seat during acceleration, differentiated perceptions of the occupants are considered. The undesired vibration phenomenon shall be reduced to a minimum to ensure a pleasant ride for drivers as well as passengers.
Although the influence of vibrations on the human body is much less when working with machines compared to driving a car: engineers should not only focus on possibly occurring resonance problems, but should also bear in mind that human beings are “resonance systems” as well.