Request ID: FOI-2986-2324 Date published: 12 December 2023
You asked
I'm working on an acoustic panel attempting to target and reduce the noise level inside the central tube underground. However, I need some critical information from TFL to understand better and design acoustic solutions.
Here are some of my questions:
1. Is the noise produced inside the central line tube mainly high frequency or low frequency? Or is it a mix of them? What is the ratio of the two kinds of noise produced inside the tube?
2. What's the noise frequency range?
3. What is the inside wall of the central line tube made of?
4. What is the current highest noise level inside the train?
5. What are some inside-tube noise reduction TFL has planned to do?
6. Are there any research opportunities for me to join or further investigate?
We answered
TfL Ref: FOI-2986-2324
Thank you for your request which we received on 4 November 2023, asking about noise levels on the Central line.
Your request has been considered in accordance with the requirements of the Environmental Information Regulations (EIRs) and our information access policy. I can confirm that we hold the information you require.
You specifically asked:
Is the noise produced inside the central line tube mainly high frequency or low frequency? Or is it a mix of them? What is the ratio of the two kinds of noise produced inside the tube?
What's the noise frequency range?
The attached table, which contains data taken on 4 September 2023, provides the levels and 1/3rd octaves in a Central line train cab recorded for the entire tunnel sections between White City and Newbury Park.
What is the inside wall of the central line tube made of?
It’s steel rings and concrete.
What is the current highest noise level inside the train?
See the attached table.
What are some inside-tube noise reduction TFL has planned to do?
We want to tackle in-carriage Tube noise by removing certain track fastenings linked to increased noise levels, and either replacing with alternative track fastenings, or installing new rail. We are exploring the use of variable speeds to understand the impact on the growth of corrugation. However, rail grinding is our primary method of addressing in-carriage levels.
Are there any research opportunities for me to join or further investigate? We don’t have anyone trying to research this topic, so I am not sure, but I wonder if Anthony and Chris feel this is something they could support from an engineering perspective?
We don’t have a study on in-carriage Tube noise on the London Underground at the moment. I have passed your email onto my colleagues who deal with this issue for their attention.
If this is not the information you are looking for, or if you are unable to access it for any reason, please do not hesitate to contact me.
Please see the attached information sheet for details of your right to appeal as well as information on copyright and what to do if you would like to re-use any of the information we have disclosed.
Yours sincerely
Eva Hextall FOI Case Management Team General Counsel Transport for London
