This may be of help.
https://www.asha.org/public/hearing/loud-noise-dangers/
Exposure duration seems to be an important consideration.“Sound-level meters measure noise levels. We record noise levels in decibels, or dBA. The higher the noise level, the louder the noise. You can listen to sounds at 70 dBA or lower for as long as you want. Sounds at 85 dBA can lead to hearing loss if you listen to them for more than 8 hours at a time.
Sounds over 85 dBa can damage your hearing faster. The safe listening time is cut in half for every 3-dB rise in noise levels over 85 dBA. For example, you can listen to sounds at 85 dBA for up to 8 hours. If the sound goes up to 88 dBA, it is safe to listen to those same sounds for 4 hours. And if the sound goes up to 91 dBA, your safe listening time is down to 2 hours.”
There are also free Db meters available for Iphone and Ipad onthe APP Store. Many are free or very low cost. It would be best to measure as close to the Toddler’s head location as possible.