Not all of the mentioned apps are free, but most offer free versions or trials. Here’s a breakdown:

Free Apps:

1. NIOSH Sound Level Meter

• Completely Free: Yes.

• Developed by a government agency, making it a reliable option with no cost.

2. Sound Meter – Decibel Meter

• Completely Free: Yes.

• Offers basic functionality without any charges.

Free with In-App Purchases:

3. Decibel X: dB, dBA Noise Meter

• Free Version Available: Yes.

• Paid Features: Advanced tools, ad removal, and calibration options.

Paid Apps:

4. SPL Meter

• Completely Free: No.

• Requires a one-time purchase, typically around $2-$5.

If you’re looking for a high-quality free option, the NIOSH Sound Level Meter is highly recommended.