The acoustic performance of wood is the sound it makes when an acoustical source, such as the body of a guitar or drum, vibrates across its surface. The soundboard of an acoustic guitar or the shell of a snare drum are examples of materials that offer enhanced acoustic performance. Wood’s natural resonance is part of what makes furniture and buildings resonant, but in loudspeakers the acoustic performance is actually worse than using different types or materials with lower resonant frequencies like paper and plastic.
Wood is an organic material, formed by a seed, growing in the ground and making it resilient against tough environmental conditions. The acoustic performance of wood comes from its resonance at around 1.1kHz (very low frequency compared to other materials) that is caused by the density of the carbon-hydrogen bonds. Acoustic performance manifests itself through sound vibrations within wood that can be caused by sound waves or a physical impact from an object like a musician’s fist or palm.
Enhancing Acoustics:
Since wood is sensitive to physical impact, the acoustic performance can be enhanced by adding a layer of another material on top, such as plastic. The layer acts as a protection barrier against the sound waves that cause resonance within the wooden wall panels. The resonant frequency of wooden materials can be tuned through the addition of different materials to add mass or dampen vibrations. The addition of weight can change the pitch of a sound by altering the mass distribution and increasing or decreasing the reactance (resistance to current). Adding damping material can act as a hard enclosure which lowers the resonance while still presenting sound waves inside.
The wood grain on a finished item of wood furniture is often used as decoration and can be a good visual aid in making decisions about which type of wood to use. The grain of each piece should also be examined to ensure that there are no unsightly defects such as cracks or warping, especially if they are hidden on the back afterpieces.
Does wood reflect sound, or does wood absorb sound?
The acoustic performance is not affected by the vibrations of sound waves moving through the state of water, ethanol or air. However, acoustic performance does depend on the frequency of the source and whether it is reflected or absorbed by the material. These factors must be considered when designing a speaker enclosure for sound waves at low frequencies where resonance has an effect in wood. According to wood’s resonance frequency and how it is amplified by the size of the enclosure, the acoustic performance can be optimized for specific purposes. A sound wave will reflect off a hard surface and bounce around an enclosed space, creating echo effects that can sound of like reverberation. Wood can be used in speaker enclosures that are acoustically enhanced to protect against sound waves.
Designing Acoustically:
The acoustic performance of wood offers practical uses. The nature of wood’s bending and compression can be used for products such as wah-wah pedals and acoustic guitars with built-in pickups. Wood’s acoustic performance is also useful in the construction and design of churches, homes and other buildings. Finding the correct resonance frequency is important for building a structure that will retain its form with minimum maintenance. The speaker system must be designed to work with the acoustic performance of wood. The shape and size of the enclosure should be well considered since it will affect the sound waves inside. Different types of enclosures can also be made to absorb sound waves for lower frequencies where resonance requires less amplification.
What properties control the quality of sound reflected by wood?
The properties of wood determine the quality of sound waves that are reflected from the surface. One property is how dense the wood’s grain is. Denser grains absorb more sound waves within the material and create a tighter resonance for larger enclosures or speakers. Other important factors include whether or not the grain is oriented vertically or horizontally, the type of material that the grain is made of and whether it has been glazed or stained to give it a surface finish. Tychonic wood has a very small grain that is oriented vertically while dendritic wood has a large grain with many smaller pieces of uniformly bent grain. The grain orientation on a piece of tychonic wood can be used as an indicator of quality. Glazing and staining can alter the acoustic performance due to the effect on how sound waves are absorbed by the enclosure.
Conclusion:
The structure of wood is a very desirable trait that can be used in many products. The acoustic performance of wood can be modified by adding weight, damping material or even layers of different materials. Wood’s properties have been given great consideration when constructing homes, buildings, churches and other structures which are designed to last over time through proper maintenance.
