Why Is an MRI So Loud?

If you have been told to expect noise during your MRI scan, you may be wondering why a machine that uses magnets and radio waves makes so much of it. The short answer is that parts inside the scanner vibrate as it takes pictures, and that vibration makes a loud, repetitive sound.

This guide explains where the noise comes from, how loud it can get, how your hearing is protected and what to expect on the day, including for children and babies. Knowing what is coming often makes the scan easier.

Where the noise comes from

An MRI scanner uses three kinds of field: a strong static magnetic field, gradient magnetic fields that are switched on and off rapidly, and radio waves. The noise comes from the gradients. The MHRA explains that when alternating currents flow through the gradient coils inside the strong main magnetic field, forces act on the coils and make them vibrate. That vibration is what you hear.

The NHS describes the result as loud bangs and clicks as the scanner takes pictures. The noise is a normal part of how the scanner works and does not mean anything is wrong.

How loud an MRI scan is

According to the MHRA guidance, noise inside the scanner can be louder than a pneumatic drill, a fire alarm or a music concert, at over 100 decibels. That is why hearing protection is a standard part of every scan.

The MHRA says hearing protection should always be made available to anyone in the scanner room during imaging, unless it can be shown that noise will not exceed 80 dB(A). It also notes that ear plugs and ear defenders can be used together, and that reduced-noise scanning techniques should be used whenever possible.

How your hearing is protected

The NHS says you will be given ear plugs or headphones to protect your ears. A few simple things help them work well:

• Ask the radiographer to show you how to fit ear plugs properly, as a loose plug lets in more sound.
• Tell the radiographer if your ear plugs or headphones slip during the scan. They can hear and speak to you throughout.
• Tell the clinic in advance if you have a hearing condition. The MHRA lists people with existing ear conditions among the groups of particular concern for noise.
• Ask whether the clinic offers music through headphones, as some do.

What to expect on the day

The NHS says an MRI scan usually takes between 15 minutes and 1 hour, but can take longer. You lie on a bed that moves into the scanner, and you need to keep as still as you can while each set of pictures is taken. The radiographer controls the scanner from another room and can hear and speak to you.

If you feel anxious, the NHS says you may be able to have a medicine to help you relax. Our guides to what to expect during an MRI scan, claustrophobia and MRI and how to prepare for your scan have more practical tips.

Children and babies

The MHRA names children and newborn babies among the groups of particular concern for scanner noise, so hospitals take care to protect their hearing. Great Ormond Street Hospital tells families that the scanner makes a continuous knocking sound that can be quite loud, and that children are given ear protectors. Children there can watch a film or listen to music during the scan, may bring a favourite toy, and a parent is usually welcome to stay with them in the room.

For young babies, some hospitals use a technique called feed and wrap instead of sedation or a general anaesthetic. Babies tend to fall asleep after a feed, so they are scanned while asleep, with ear protectors to reduce the noise. If you are thinking about a private scan for a child, our guide to private scans for children explains what to ask.

If you are pregnant

The NHS safety questionnaire asks whether you are, or could be, pregnant, so always tell the clinic. On noise specifically, the MHRA guidance explains that an unborn baby is protected from normal sound transmission by the surrounding amniotic fluid and the fluid in the ear. Whether and when to scan in pregnancy is a decision for the clinical team.

Having an MRI privately

MRI does not use ionising radiation, so IR(ME)R does not apply. Many private clinics accept self-referral, usually after their own safety screening, but each clinic sets its own policy. If noise or anxiety is a concern, ask the clinic about ear protection, music and how it supports nervous patients when you send an enquiry. You can see MRI clinics near you on FindScan and compare each clinic's own listed price.