Today weâ€™re going to talk about what are the difference between Axial, Tangential and Oblique modes. We get a lot of people sending us emails and asking you know â€˜What are these differences you refer to in your analysis?â€™ Well the axial modes are the pressure areas that occur between two parallel surfaces, so we could have pressure between two sidewalls.

We have pressure between the walls because those are two parallel surfaces and then donâ€™t forget about the floor and the ceiling. We have pressure that exists between those but those are called something else. So axial pressure, axial modes are the pressure areas that occur between two parallel surfaces, thatâ€™s the optimum word here.

Tangential is between four walls, so we have pressure that occurs between the two parallel walls and then two more parallel walls, thatâ€™s the definition of tangential. Axial pressure is always much stronger than tangential. Tangential pressure is always much stronger than oblique, oblique is between all six walls. So we have ceiling, floor and then we have front, sides and rear wall. So we have three sets of pressure areas going on within the room. Well if you think about it the room has six sides so itâ€™ll produce three sets of energy relations.

So itâ€™s all dependent on the dimensions and itâ€™s all dependent on the frequency thatâ€™s going to cause a resonance. A 30 cycle wave of energy will produce a different resonance in a different room than a forty will just because of the length of the wave. So all of these variables have to be taken into consideration and the strength of that resonance is dependent on the distance, obviously the smaller distance and the bigger wave is going to create more pressure. But the pressure between two walls is always the greatest.

So when you send in your room dimensions to me I always give you a report with these three pressure areas and I tell you what frequencies your problems are at. But your axial pressure, and Iâ€™ll note this on the analysis, is always going to be the stronger of the three. So itâ€™s the air that moves between these surfaces that causes the sound and the resonance. Itâ€™s not the structure itself although it can be bit. In most case itâ€™s the air being confined between two parallel surfaces, two sets of parallel surfaces and then all six surfaces that causes the problem, thank you.

In Summary

Thanks and speak soon
Dennis

I am an acoustic engineer with over 30 yearsâ€™ experience in the business. My technology has been used in Electric Lady Land Studios, Sony Music of New York, Cello Music and Films founded by Mark Levinson, and Saltmines Studios in Mesa, Arizona, along with hundreds of others.