What is Sound?

Sound is the name that we give acoustic energy, and while the study of acoustics is complex, conversations about it don’t have to be.


Acoustic energy causes an object to vibrate, and when it does, it creates fluctuations in atmospheric pressure surrounding it—like a tuning fork. Atoms and molecules surrounding the object become excited and transfer that energy away from the source, and as that wave of energy reaches our ears, we experience it as sound. When sound becomes unwanted or overwhelming noise, it can have adverse physiological effects.

These pressure, or sound, waves can travel through all types of mediums, liquids, solids, or gas. The medium that the energy passes through influences the direction that energy takes. Waves in the air are described as being ‘longitudinal’—where the energy between particles compresses together and then expands in the direction of travel. In liquids and solids, more complex forms of energy transfer are possible.

The medium also affects the speed of sound—sound travels more quickly when atoms and molecules are closer with stronger bonds. This means that sound in the ground travels faster than it does through the air.

The speed of sound is tied to its ‘frequency’ (the rate of vibrations) and its ‘wavelength’ (the length of the pressure wave). Because the speed of sound in a single medium does not change except in extreme situations, a change in frequency has an opposite effect on wavelength—if the frequency goes up, the wavelength goes down, and vice versa.

Sound frequency is usually described using terms like rumbly or bass-y, buzzy, and hissy. Sounds can be tonal (focused on specific frequencies) or broadband (across a wide range of frequencies).

The frequency of vibrations falls somewhere on a continuum from infinitely slow to exceptionally high rates per unit of time. This continuum is where the measurement Hertz (Hz) comes from: rate of vibrations per second. Very low rates (up to around 100 Hz) can be experienced physically and are generally described as vibrations. Higher frequencies (between 16 Hz to 20,000 Hz) are experienced audibly as sound.

Sound level describes the perceived ‘loudness’ of a sound pressure wave. People will sometimes describe loudness as power or intensity when speaking in general terms. When talking about acoustics, these three metrics are related but different. Only sound pressure can be measured directly. Sound power describes the total acoustic potential of a source, and sound intensity considers the acoustic potential across an exposed area.

Parklane works within a holistic framework to achieve a ‘quieter’ outcome. To create an effective solution, we need to understand how much sound pressure needs to be mitigated and the frequency characteristics of the noise sources. It’s all part of the Parklane Process.


The Parklane Team

For assistance with your noise or vibration control challenges, contact a member of our team.