Modular Panels or a Welded Shielded Room? Pros and Limits
We compare shielded rooms built from bolted modular panels with welded steel rooms on performance, installation time, portability and cost.
3 min readOctober 26, 2026
dB Is a Ratio
The decibel (dB) expresses the ratio between two values logarithmically. In shielding, the two values are the signal level outside and inside the room. 20 dB means the signal amplitude falls tenfold; 40 dB a hundredfold, and 100 dB a hundred-thousand-fold.
In terms of power the difference is even larger: 100 dB means one ten-billionth of the outside power reaches the inside. So while the difference between 80 and 100 dB looks small, it is actually a hundredfold difference in power.
dB Means Nothing Without Frequency
A room's shielding value changes with frequency. It drops for magnetic fields and very low frequencies, while at high frequencies the quality of the door and penetrations decides. A single dB figure can't be compared unless the frequency it was measured at is stated.
That's why shielding should be given in quotes as a table or curve with the frequency range, for example 60 dB magnetic field at 10 kHz and 100 dB plane wave at 1 GHz.
The Test Method Changes the Result Too
The same room can give different results when measured with different methods. Antenna distance, choice of measurement points and the equipment's dynamic range affect the result. That's why a method such as EN 50147-1 or IEEE 299 should be stated with the value.
The measurement system's dynamic range must exceed the value being measured. If a system meant to measure 120 dB doesn't have more than 120 dB of dynamic range, the result only shows the system's limit.
How Many dB Is Enough?
To reliably block phone and Wi-Fi signals, 80–100 dB is often enough. TEMPEST, military and EMC test applications require higher values and wider frequency ranges.
The right target depends on the ambient signal level and the sensitivity of the equipment to be protected. We propose a realistic target after measuring the environment during the survey; our specification writing guide explains how to express this value.
Frequently Asked Questions
Is 120 dB always better than 100 dB?
Yes, if both were measured with the same method at the same frequencies. Values given with different methods can't be compared directly.
Does the dB value drop over time?
Gasket wear and a misaligned door can lower it. Annual measurement and maintenance preserve the original value.
Why are lower values given for magnetic fields?
Attenuating low-frequency magnetic fields is physically much harder and requires different materials.
Related Solutions
Let's Find the Right Solution for Your Project
Get a QuoteYour free site survey and quote will be ready within 24 hours.