## bad teachers.. or should that be engineers!

Make no mistakes, teaching is a hard profession, particularly when there is a chance that some in the class don’t want to learn.

Degree level, should be easier and postgraduate even easier as there should be filtering to ensure the class contains people who want to be there and more importantly have paid to be there!

I’ve recently been asked to review a MSc in acoustics both in terms of course content and teaching and report back to the endorsing body, what I saw annoyed me & resulted in me having a stand up argument with the tutor.

The issue which caused this was reverberation time, a fundamental of any acoustics course. There are many formulas for calculating the reverberation time of a space, depending on how complex you wish the model to be, but they are all based on some very good work by sabine at Harvard university.

Sabines basic formula for predicting reverb time was based on empirical measurements but cam be explained by a theoretical understanding of Browning motion and is given by:

RT60 = 0.16 V/A

Where V is the volume of the space and A is the absorption in the space

A = s1a1 + s2a2 + … snan

Where s is the absorption coefficient of the material and a is the area of the material.

The absorption coefficient is a boundry coefficient where 0 is a perfect reflector and 1 is a perfect absorper, corresponding to free space (no boundary)

What caused the issue was that the lecturer insisted it was possible to buy a product that will lower the RT60 of the room by having an absorption coefficient greater than one.

It is! And I know of plenty of examples I can buy.

However I queried this with him because with a basic grasp of physics this allows the conservation of energy to be defied… not something I expect a teacher to be teaching!

The situation arrives because the way we engineers have allowed a loophole in the measurement technique; this technique means it is perfectly possible to buy something that defies the fundamentals of physics.

The teacher believes his students wouldn’t understand that, I remember being taught various models of atoms and being told with each “this is incorrect, it goes beyond this but you couldn’t comprehend it yet, this model gets you past this level & if you want to know more take the next level”

if the teachers opinion is true I don’t believe his pupils should be classified as engineers, but the question is …

Should I be more annoyed at the teacher who I gave a fair chance to clarify his statement and I believe was teaching dangerous ideas or at the standards bodies for allowing & refusing to close an obvious loophole?

Standards bodies care, but the underlying issues at stake, tradition, money ,and power go far beyond the physics involved and exert far greater force than the need for technical accuracy.

I also understand the teachers view too, coming out and saying “this is incorrect, but…” can be a motivational killer for all but the most dedicated students. On the other hand, if this was a MSc program ????

Ron Amundson said this on March 28, 2011 at 4:38 pm |

What annoyed me is that whilst I can understand presenting the course material in a particular way I struggle with this as an answer to a question, particularly in an engineering course…. It left me with overwhelming imagery of Gerald Scarfes cartoons of the school in “The Wall”

I agree with your summary of the forces & motives surrounding Standards and Standards are incredibly useful but on an all too frequent basis I see them used as a “Nuremberg defense”

elektroacoustics said this on March 28, 2011 at 6:39 pm |