studio tech - week 1 (sound)

This week's lessons focused on the basics which are about sound waves, what are they constructed of and how do they actually produce the different sounds we hear from different settings of instruments. Topics covered include properties of sound waves, issues faced in an acoustic studio setting and how to treat them as well as learning about overtones.

The three main properties of a sound wave are amplitude, frequency and wavelength. Amplitude is the value of the peak/trough and for sound waves, it is the extent to which air particles are displaced, and this amplitude of sound or sound amplitude is experienced as the loudness of sound. Frequency is the number of wave cycles occurred in one second, which eventually calculates the speed of the vibration, thus determining the pitch of the sound. Wavelengths are the distance between two peaks/troughs. The shorter the wavelength, the higher the frequency, and the higher the pitch. In other words, short waves sound high; long waves sound low.

Common issues faced in an acoustic setting room would be standing waves, which are produced whenever two waves of identical frequency interfere with one another while traveling opposite directions along the same medium. Though knowing the definition, I still wasn't quite sure what standing waves exactly are without identifying an example of it.

To my understanding at this stage, standing waves, which are also known as room modes, have an effect on certain frequencies when it experiences constructive waves (frequencies will be amplified twice as loud, louder note) while de-constructive waves, due to echo, cancels out certain notes, in a setting where each of these scenarios will happen at different location of the room. To treat this, resonant and porous absorbers can be used on walls.

Flutter echo on the other hand happens whenever there are parallel reflective surfaces. The sound repeatedly bounces off each wall and creates a series of bright echoes. I also discovered more about different groups of reflections, including early reflected and late reflected sounds. The early reflected sound leaves the loudspeaker and then bounces off one of the boundaries of the room before reaching the ears of the listener. Late reflected sounds are those that arrive at the listener’s ears after multiple reflections. The speaker and room both contribute to what we hear as late reflected sounds. The speaker’s contribution is termed sound power (aka acoustic power, the rate which sound energy emits, travels or reflects/unit time). "The room contributes its decay properties, both at mid-to-high frequencies (reverberation) and low frequencies (room resonances)." (Source: http://www.acousticfrontiers.com/early-reflections-101/) Treatment for early reflections may include adding absorption & diffusion at the first reflective points.

Lastly, bass buildup at the corner of rooms are also a form of issues where low frequencies tend to be centered and built up there due to reflections, causing lack of clarity sounds. Diffuser can be used to scatter sound waves. While reflective surfaces create liveliness in a dead/dry room, too much of it can cause all the issues listed above (room modes, early reflections, bass buildup & flutter echo).