Information About the Device
The device is a Lenovo ThinkPad T430.
I am not the original owner of this device. It was provided to me by my boss, but it looked like it had never been used much(physical appearance). I inspected the interior of the device, after I noticed the unusual fan noise compared to my previous laptop experiences. The fan was clean and I replaced the thermal paste of the CPU. I ended up keeping this laptop as a gift from my boss.
Graphics: The motherboard I have only has the integrated Intel HD 4000 graphics. There is no discrete GPU on this device.
Storage: I only run SSDs nowadays, so the only component responsible for audible noise is the fan.
I am not certain.
BIOS: I am not certain about the BIOS version when I got the device or even if I updated it back then (first quarter 2014).
My Specific Needs
I have to use my laptop in libraries, office environments and construction settings. The latter is not particularly relevant to the issue, but it goes without saying that I need my device to be quiet sometimes even if I am running CPU intensive tasks such as dealing with source code, MATLAB, etc. . I also use flash and video/audio streaming abundantly and the fan sound will compete with the sound from the internal speakers.
I use mostly Windows 7, Windows 10 and Debian GNU/Linux across different disks.
Describing the Issue
This one is a bit hard, since it is subjective, depends on specific needs and expectations.
Starting the device makes the fan rapidly accelerate for a second. This could be described as an unusually fat fly lifting off from a table and having an hearth attack while in the middle of it's flight. Otherwise, it can be described as a pick-up truck starting off. Whichever fits your liking. To be serious, my understand of the physics involving sound is very limited, but I can tell there is a very fast variation in pitch that is responsible for the annoyance factor of the sound. I say this because it does not even need to be very loud to gather your undeserved attention.
Of course the start-up of the device is a minimal issue. The operation under CPU/GPU load is what might get more frustrating with time, even if you ignore it initially (I ignored it for about one year and half).
Some Pseudo Science
I can tell you the temperature was not a particular issue. If the device was idle, the fan would at times just sit still due to how cool it was and the only activity that actually raises temperatures above 85º C is using flash for video streaming or other computational heavy programs. The rotation rate of the fan adjusted to the temperature correctly in my perspective.
I did use ThinkPad Fan Control as suggested by pretty much every forum I visited about this issue, both on Windows and Debian (using the repository packaged version). This piece of software does very little to combat the pitch variation, but it is a very nice tool to use as reference when comparing across devices of the same model with similar hardware or in case of sensor malfunction.
I upgraded the BIOS to the latest version supplied on the Lenovo Support website on October 2015, just a few days before making my decision to change the fan. It did not change anything in my opinion. However there are reports of this fixing some issues for the T430, but from what I have understood it about temperature and temperature sensors.
Replacing the Fan
Since Lenovo has a very lacking presence in Portugal, I decided to just skip a step and order a different model fan from an online retailer (also because these kind of parts are pretty difficult to find in my country). I got an hint from the Lenovo forums that the model KSB0405HA fan from Delta Electronics, Inc. would be fit for the job. Since I did not find this part by itself online I had to order the full fan assembly which includes the cooling copper pipes. I managed to only find it available in the United States of America on Ebay, so I got the privilege of paying double for the fan due to shipping + handling (around 35$USD total).
One particular difference is that there is an additional cooling pipe that would fit over the discrete GPU that I do not have, but it fits nicely inside the device. One noticeable visual difference between over the FRU P/N 04X3787 fan that I had, is the width of the carvings on top of the housing for the fan (I imagine this might necessary for air intake). They much more wide on the Delta Electronics fan.
Replacing the fan is a relatively simple process, if you are not planning to rush it. I followed: T430 Fan Removal Guide - MyFixGuide , but I believe also supplies similar instructions somewhere in it's support website.
WARNING: I am not sure how this may affect the validity of your warranty.
Comparing the Noise
There is very little mutual ground. The pitch variations are clearly unnoticeable (at least to the ear).
The start-up air flow sounds like a happy little puff of air and is not audible most of the time.
I did not measure decibels or make any attempt to make a recording of the sound while using ThinkPad Fan Control on specific levels so I could compare it later.
It sounds just like what you would expect from air blowing through a window or other small gap.
It is much more bearable when running the fan disengaged in TP Fan Control.
The fan is inaudible much more often than it was before in an office environment.
I did not manage to compare temperatures with both fans due to my own lack of know-how and using different thermal paste and cooling system, but there is no major change in the triggering of specific fan rotation rates, CPU load and CPU temperature.
I hope this is usefull to someone, since it has already been a few years since the device was launched.
Have a good day. 
Hi,
It seems that if your Thinkpad T430 is equipped with Fan&Heatsink with the model S/N : 0B41086 it's the wrong one because the lower side of the fan has the surface of the air intake grills very very small compared to the model S/N : 0B41087, so the fan cannot take enough air to blow it into the heatsink fins to cool it properly.
I have the last model and it does the job done even if I have my T430 equipped with a i7-3610QM 45W quad-core CPU.
Hope I helped.
