Strange results. Comparisons of measurements and simulations. When to use Global- and Quick- Estimate or Point-/multipoint- and Grid- Response.

Q: Can I use the sources in Odeon as background noise for STI-calculation?

A: When calculating Speech Transmission Index in Odeon you need to type in a total background noise level, into the Room Setup. The video below shows how you can use sources in ODEON to find this total background noise level.

Q: Is SPL the same as Strength? I couldn't find G in the Energy Parameters.

A: The Strength G (as defined in ISO 3382) is the same as the SPL if:
- One (and only one) omni-directional sound source is turned on, and
- the overall gain in the point source editor is set to 31 dB.
In this case the bottom line in the point source editor will display a value of 0 dB for the SPL on axis at 10 m. This is exactly the reference of the Strength, G. So, all calculated SPL results are actually also G values.
However, in all tables and graphs you will only find the symbol SPL, even when the conditions for G are fulfilled.

Q: The stage parameters STearly and STlate do not appear in my single point response?

A: Make sure source and receiver has mutual distance between them of 0.9 to 1.1 m

Q: How do I calculate STI with a certain signal to noise ratio SNR?

A: For calculation of STI with a certain Signal/noise ratio, calculate the SPL in your receiver point (read result in Energy parameters in Single Point Response). Then set the background noise to this level +/- your background noise SNR. Then when you calculate the Point response again, the STI is calculated with the desired background noise.
When making an auralisation with the same S/N – it is more complicated among things because the signals used for auralisation of voice and noise may not have the same ‘energy’ contents and because the playback level (SPL) on the headphone is not a simple matter to adjust to an absolute value. Probably the best way would be to actually measure the SPL from the headphone using a dummyhead or an ear coupler. As In the Auralisation chapter in the Manual “Adjusting levels there is an alternative suggestion.”

Below video shows how you can use sources in Odeon to find this total background noise level and ad the background noise level in an STI calculation.

Q: Can I calculate the sound pressure level in a receiving room using the reduction index in an Odeon-simulation?

A: The input you can use for simulating sound transmission in Odeon is the sound reduction Index for a certain type of wall.

Odeon does not take into account flanking transmission.

You can use Odeon for simulating sound pressure level in the receiving room from a well defined source, if the flanking transmission does not play the most important role in your construction, compared to e.g. the room acoustic complexity of the rooms. If you know the influence of the flanking transmission you can manually include it in the sound reduction Index for the wall.

It is important to check the reflection density in the receiver room. (You do that from a point response / reflection density). It should be more than 50 if you want good results. If it is less you should increase the number of rays.

To make simulations according to measurement standard, remember to use the required amount of sources and receivers.

Video describing how to simulate sound transmission.

Q: I get negative values of SPL in places, where I would expect sound pressure to be noticeable?

A: Check 3DopenGL and ray tracing if the point-, line- or surface- sources are inside the room and transmitting most of the sound energy into the room. Make also a 3DopenGL check of the receivers. If using a grid map it is possible to exclude receivers outside of the room from being displayed in 3DGrid when the chosen parameter is over or under a selected range. This is set in the Options/Program setup/Grid colours.