The speed that sound waves travel, largely depend on the material type. This is why, for example, sound cannot travel through a vacuum at all. At Structural Diagnostics Inc, we are intimately familiar with the properties of sound and how it is the best tool for examining many substances without causing them permanent or even temporary harm. Let’s take a look at some facts about sound and the waves it produces to give you a better understand of why and how it works as an effective tool for analyzing aircraft parts and systems.

What is Sound?

It may seem like a ridiculously obvious question but it is not. For centuries man has been studying the properties of sound. However, for our purposes sound is a pressure wave which is created by a vibrating object. These vibrations in any surrounding medium – let’s say air – are set into vibrational motion. This essentially is a form of energy being transported through the chosen medium. As most people know, sound can thus travel through gas, solids or liquids but does so at different rates due to the molecular density of these mediums. Here is a look at the speed of sound through various mediums.


Material                     Speed (m/s)

Air at 20 degrees Celsius         343 m/s

Air at 40 degrees Celsius         355 m/s

Helium                                                    972 m/s

Hydrogen                                 1,286 m/s


Material           Speed (m/s)

Mercury           1,450 m/s

Water               1,493 m/s

Sea water         1,533 m/s

Glycerol           1,904 m/s


Material   Speed (m/s)

Copper             4600 m/s

Brass    4,700 m/s

Steel     5,050 m/s

Aluminum       6,320 m/s

Diamond          12,000 m/s


How sound reacts to create images that can be used in ultrasonic testing depends greatly on the material it is travelling through. This is why it is important to know about the materials you be using our equipment on. With sound you can get a detailed picture of the materials you are testing and this data can help you make informed decisions that impact your company. People in construction, medicine and of course the aerospace industry have known this for years. Our company provides high tech equipment such as our ultrasonic gantry system and our ultrasonic bubbler system to keep your craft up to specs.