Overview

Sound intensity is how loud something is as a measurement (measured in decibels).

Loudness is a subjective term and unique for each person.

Sound itself is a tricky piece in the built environment because even though we have sound intensity to measure levels of sound… Sound is very relative, and has many factors to consider such as distance, age of the listener, and number of sources. Therefore, it’s one of those things that will vary from person to person and why sound can be so tricky on a project.

Sound Intensity

By definition, 0 is no sound, with 1 being essentially the threshold of human hearing. On the upper levels, 130 to 140 decibels is the threshold of pain. Decibel levels past 160 aren’t typically experienced in the natural environment.

Below you will find a chart encompassing typical values for different decibels (dB).

Sound Chart

180	130+ Immediate Damage to Hearing	(180) Estimated Krakatoa Volcanic Explosion
170
160		(160) Jet Airplane
150
140		(140) Pain Threshold
130	120-130: Damage after 7.5 minutes
120		(120) Rock Concert (wear earplugs!)
110	100-120: Damage after 2 hours
100		(100) Subway Train
90		(90) Lawn Mowers (High end)
80	85+ Threshold of Safety; OSHA Regulated above this level
70		(70) Normal Office Noise
60	50-60 Comfort Range for a Person	(60) Normal Conversation
50		(50) Kitchen Level Noise
40
30	0-30 (Max) for sleeping and study areas	(20-30) Light Whisper
20
10		(10) Normal Breathing
0		(1) Threshold Of Hearing

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Most Intense Sound?

The 1883 volcanic eruption of Krakatoa (Indonesia, form. Dutch East Indies) is thought to be the loudest sound ever heard. The eruption is estimated to have reached 180 dB, loud enough to be heard 3,100 miles away, while rupturing the eardrums of sailors on a vessel off the coast of Sumatra (approx 40 miles away). The resulting pressure wave rounded the globe three and a half times (verified by barographs worldwide).

It should be noted that the explosion being heard 3,000 miles away was across water where there are obviously less obstacles to disrupt the sound. Over land, the explosion was heard approximately 1,900 miles away in Australia.

Perspective:

• Los Angeles, California to Bangor, Maine is ~2,900 miles as the crow flies. (image above)

Loudness

The sensation of loudness is subjective. There are guidelines and standards to help determine the usefulness of increased or decreased decibel levels in architectural situations. It’s important to consider the perception of change because the change perceived may not be worth the money spent to implement the change.

Logarithmic

Addition of Sound Values:

Because sound is logarithmic, you cannot simply add together different sounds and create a new sound. A logarithmic scale is one that increases by % rather than a set value.

Computer Lab Example

To help understand this, think about a computer lab at a school. Each computer may make a small amount of noise; call this minutia amount to be 5 decibels of sound for each computer. If there are 30 computers in the room, all running, there is not (30*5) 150 decibels worth of sound loudness (roughly equivalent to a jet airplane).

To find the exact amount, you can use calculations, however, it’s easier to estimate the value using guidelines that can come very close (within 1%) to the real value without the arduous calculations and are much quicker.