This is a linguist who is not a member of the church testifying that the book of mormon was originally written in some semitic language.
The best account
https://unblogmysoul.wordpress.com/2014/06/24/die-boek-van-mormon/
At the bottom of this page you can find the transcript of the stake meeting in the church history library:
* Terri’s note: For anyone interested, the current location of the transcript for the May 14, 1972 Transvaal Stake meeting in Johannesburg is in the Church History Library, call number LR 9256 24, Folder 1.
I found a link to the recording and transcript!: https://catalog.churchofjesuschrist.org/record/bec5cabc-c97b-4b8b-9d30-b4627b2321d4/0?view=browse
This is the meeting in which the linguist testifies in his own voice.
A copy of that account without as much text
https://smalltalkbillross.wordpress.com/2012/05/06/die-boek-van-mormon/
Another reference to the first account but with an interesting comment in the comment section
That third link contains a comment in the comment section in which someone says they personally know another person who was present in the meeting and that they said this account is true.