Object ID: 00000018WIA3089B770GYZ
Topic ID: id_40025535 Version: 1.3
Date: Jul 26, 2022 1:40:08 PM

Acoustic noise

Another potential safety issue associated with gradient switching is the loud noise. The rapid alternations of currents within the gradient coils cause the coil assemblies to vibrate against their mountings, thus generating a loud resonant noise. The acoustic noise produced during scanning can exceed 99 dBA in the bore.

Warning

The sound level at the operator’s console should be limited to comply with local rules.

Warning

Hearing protection is required for all people, including the MR worker, in the magnet room during a scan to prevent hearing impairment. Acoustic levels may exceed 99 dBA. Patient hearing protection with a noise reduction rating (NRR) of 29 dB or better is required to reduce acoustic level below 99dBA. The A-weighted RMS sound pressure level is measured according to NEMA MS 4: 2010.

CAUTION

All personnel should be trained on the proper use of hearing protection.

Special attention should be utilized to protect the hearing of neonates, premature infants, and any other condition that does not allow for hearing protection to be applied.
Patients with increased anxiety may have a lower acceptance to sound pressure (e.g., newborns, infants, young children, elderly, and pregnant women and the fetus).
Anesthetized patients have less then normal protection against high sound pressure. Hearing protection should not be omitted.
Typical operator console noise levels are below 60 dBA, so hearing protection is generally not required at the operator console. However, it is important to ensure the sound level complies with all local regulations.
In some countries, legislation exists that limits employee exposure to noise levels. Ensure compliance with your local regulations by providing additional hearing protection to MR workers for use in the magnet room where required.
If a music sound system is in use by the patient during scanning, the music sound system must provide > 29dB NRR of attenuation. All hearing protection devices must provide > 29dB NRR of attenuation.

Encourage the routine use of earplugs to prevent problems associated with acoustic noise during MR procedures. GE offers disposable ear protection of various noise reduction ratings. These can be ordered through the GE accessories catalog. The table below, describes the available types of disposable ear protection.

Table 1. Disposable ear protection
Description	dB
E8801BA EAR Disposable Foam Earplugs	29
E8801BB EAR Taperfit2 Foam Earplugs	32
E8801BC Max-Lite Foam Earplugs	30