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I have a little bit of noise that I'd like to eliminate. It only bothers me in the dead of night, but at that time complete silence is a true blessing.

My Macbook Pro has a spinning disk and two fans. I'd like to stop each (both fans and the disk) independently, even for just a few seconds, to determine which is producing what tone of sound.

With smcFanControl I can raise the fan speed. Is it dangerous to stop the fans for even 5 seconds if I'll be running absolutely nothing (besides the base OS)? Is there a command-line hack to force this to happen?

Under Energy Saver in the Preferences I already have "Put hard disks to sleep whenever possible" checked. But it doesn't seem that that sleep-mode ever kicks in. How can I nudge the disk to stop for a few seconds?

An experiment is to replace the spinning disk with an SSD, and I may be heading in that direction anyway, but I'd like to confirm whether the fans are the culprit and that another solution (putting the Macbook Pro in the printer drawer? Getting a fanless MacBook?) will remain anyway my target before just spending time and money on the experiment.

  • This might be a silly question, but is there a reason to have the computer running all night, instead of putting it to sleep? Is it a server? – Darkstar Feb 13 '16 at 23:03
  • @Darkstar It's not a server. It just so happens that coding inspiration hits at random hours, including late at night. I do put the Macbook to sleep once I'm done. – Calaf Feb 15 '16 at 14:37
  • Yes I hear that. The fan will usually be a constant source of white noise, so the SSD to replace a noisy hard drive would be the best alternative. It is dangerous to turn off the fan in a Mac due to the tight tolerances. – Darkstar Feb 15 '16 at 22:43
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As mentioned in my comment, your best bet to reduce noise would be to migrate to a computer with an SSD drive or replace the drive in your existing computer. The noise from a standard hard drive is highly variable, while the noise from a fan set at a constant speed with fan control software would be white noise.

In regards to turning off the fan entirely, that would be risky as the Mac not only has tight tolerances that allow heat to build up quickly when the fan is off, but the OS on Macs has regular cron jobs that kick off in the middle of the night- jobs which can cause the CPU to spike in use and generate heat.

A better bet is to just keep the fan on a constant, but lower speed using fan control software. Say around 1500-2000 rpm.

That plus an SSD should allow you to have manageable sound levels, while retaining the performance of a full MacBook Pro, as opposed to the less powerful fanless MacBook or MacBook Air.

For the near term verification need, I'd recommend:

  1. going to a local electronics store with a minimum 14 day return policy (Amazon would also work), purchasing an SSD drive and a hard drive enclosure
  2. Then install the SSD drive in your computer and the old hard drive in the external enclosure
  3. Then manually install Mac OS X to the new SSD and, using the external enclosure, restore your data to the new SSD drive from the old hard drive.
  4. monitor the sounds levels over a week or so to see if they've improved.
  5. If not, then you can swap the hard drives and use the external enclosure as a means to allow you to wipe the new SSD. Then you can return both of them to the store.

If you really want to risk your system's stability and potentially cause damage, you cannot use Mac OS X, as Apple has it locked down to prevent turning off the fans.

If you can dual boot with Windows or Linux with boot camp you can use the app called "speedfan" in Windows or a terminal command in Linux, "pwmconfig". Both of those might allow you to turn off the fans completely, but at a risk of system damage.

  • The Macbook is in an office room, not my bedroom. I also put the Macbook to sleep before sleeping myself. I am trying to isolate the noise coming from the hard disk from the noise coming from the fans. Then I'll be ready to decide what to do. Can you suggest how to perform this isolation? – Calaf Feb 16 '16 at 18:40
  • The only way I've find to do that in a safe manner was to replace my hard drive with an SSD. Once I did that, I found that the noise on idle was much less and when it did occur was consistent. While there are ways to turn off the fans completely, with the tolerances in a MacBook being so tight, that is a risky move as heat will build up fast. – Darkstar Feb 16 '16 at 20:34
  • Updated my answer to refer to recommended investigatory approaches – Darkstar Feb 16 '16 at 20:50
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You can use free Macs Fan Control app to set minimum RPM for each of your fans, this will make them almost noiseless.

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What I understand from your question is that you are trying to determine whether it is your TSM HDD (traditional spinning media) or your fan that is making the noise.

The easiest way to do this is to remove the HDD and replace it with...well nothing.

Step 1: Remove the HDD.

This is pretty easy. Simply remove the screws on the bottom case of your MBP. There are 10. Make note of the top 3 going from right to left as they are much longer than the rest.

MBP Screw loctions

Once inside, you will easily the see the fans and the hard drive. Remove the bracket holding the hard drive in place and then disconnect the SATA cable connecting the drive to the logic board.

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Step 2: Boot your machine

Reset your NVRAM (Comand+Option+P+R while turning on your computer). Your fans should spin up to max for a few moments.

You can also boot into Diagnostic mode (Hold the D while booting). It will test your fans and spin them up to max for a while.

Don't worry about not having a HDD installed, nothing is going to happen. In fact, you are going to boot it with the bottom facing up towards you. What's on the screen doesn't matter for this.

Step 3: Listen for the noise.

If you hear it, you can flip over the unclosed MBP and listen to the fan closely. If you hear noise, it is most likely it. Put your finger on the fan to stop the blade. If the noise goes away, there's your culprit.

If all is quiet, time to check the HDD

Step 4: Check the drive (if required)

Reinstall the hard drive and its retaining bracket but don't close the bottom. Reboot following just like you did in Step 2. You can boot it with the bottom off and the lid open. You are more concerned with the goings on inside rather than what is on the screen. You won't be able to stop the drive from spinning, but you will be able to hear it much more clearly with it open. If it is making noise, that is your culprit and you will want to change it right away.

I just this week upgraded my MBP (late 2009) to an SSD and not only is it quieter, and cooler, it is blazing fast. In my instance, the HDD made a really horrible noise then the MBP stopped working. Here's the drive I used; it installed in about 10 minutes max. I did a clean install of El Capitan then transferred my over only my data; I opted to reinstall my applications.

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