X0306 4 2021-02-17 1 0001656536 Decibel Therapeutics, Inc. DBTX 0001722201 GV 2016 GP, L.L.C. 1600 AMPHITHEATRE PARKWAY MOUNTAIN VIEW CA 94043 0 0 1 0 0001722204 GV 2016 GP, L.P. 1600 AMPHITHEATRE PARKWAY MOUNTAIN VIEW CA 94043 0 0 1 0 0001721789 GV 2016, L.P. 1600 AMPHITHEATRE PARKWAY MOUNTAIN VIEW CA 94043 0 0 1 0 Common Stock 2021-02-17 4 C 0 321978 A 321978 I By GV 2016, L.P. Series A Preferred Stock 2021-02-17 4 C 0 5000000 D Common Stock 321978 0 I By GV 2016, L.P. The Series A Preferred Stock converted into shares of the Issuer's common stock, $0.001 par value, on an approximately 15.529:1 basis automatically immediately prior to the closing of the Issuer's initial public offering. The Series A Preferred Stock had no expiration date. The reported securities are held directly by GV 2016, L.P. GV 2016 GP, L.P. (the general partner of GV 2016, L.P.), GV 2016 GP, L.L.C. (the general partner of GV 2016 GP, L.P.), Alphabet Holdings LLC (the sole member of GV 2016 GP, L.L.C.), XXVI Holdings Inc. (the sole member of Alphabet Holdings LLC), and Alphabet Inc. (the controlling stockholder of XXVI Holdings Inc.) may each be deemed to have sole power to vote or dispose of these shares. Each of GV 2016 GP, L.P., GV 2016 GP, L.L.C., Alphabet Holdings LLC, XXVI Holdings Inc., and Alphabet Inc. disclaim beneficial ownership of the shares except to the extent of any pecuniary interest therein. /s/ Winston Macaraeg, Attorney-in-Fact 2021-02-17