Sec Form 3 Filing - Third Rock Ventures III, L.P. @ Decibel Therapeutics, Inc. - 2021-02-11

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Third Rock Ventures III, L.P. 2. Issuer Name and Ticker or Trading Symbol Decibel Therapeutics, Inc. [ [DBTX]] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O THIRD ROCK VENTURES, LLC,, 29 NEWBURY STREET, 3RD FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 02/11/2021 (Street) BOSTON, MA02116 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 47,169 D ( 1 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Series A Convertible Preferred Stock ( 2 ) ( 2 ) ( 2 ) Common Stock 2,938,945 D ( 1 ) Series C Convertible Preferred Stock ( 3 ) ( 3 ) ( 3 ) Common Stock 98,929 D ( 1 ) Series D Convertible Preferred Stock ( 4 ) ( 4 ) ( 4 ) Common Stock 54,642 D ( 1 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Third Rock Ventures III, L.P. C/O THIRD ROCK VENTURES, LLC, 29 NEWBURY STREET, 3RD FLOOR BOSTON, MA02116 X Third Rock Ventures GP III, L.P. 29 NEWBURY STREET, 3RD FLOOR BOSTON, MA02116 X TRV GP III, LLC 29 NEWBURY STREET, 3RD FLOOR BOSTON, MA02116 X LEVIN MARK J 29 NEWBURY STREET, 3RD FLOOR BOSTON, MA02116 X STARR KEVIN P 29 NEWBURY STREET, 3RD FLOOR BOSTON, MA02116 X TEPPER ROBERT I 29 NEWBURY STREET, 3RD FLOOR BOSTON, MA02116 X Signatures /s/ Kevin Gillis, Chief Operating Officer of TRV GP III, LLC, general partner of Third Rock Ventures GP III, L.P., general partner of Third Rock Ventures III, L.P 02/11/2021 Signature of Reporting Person Date /s/ Kevin Gillis, Chief Operating Officer of TRV GP III, LLC, general partner of Third Rock Ventures GP III, L.P. 02/11/2021 Signature of Reporting Person Date /s/ Kevin Gillis, Chief Operating Officer of TRV GP III, LLC 02/11/2021 Signature of Reporting Person Date /s/ Kevin Gillis by power of attorney for Mark Levin 02/11/2021 Signature of Reporting Person Date /s/ Kevin Gillis by power of attorney for Kevin Starr 02/11/2021 Signature of Reporting Person Date /s/ Kevin Gillis by power of attorney for Dr. Robert Tepper 02/11/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )These shares are directly held by Third Rock Ventures III, L.P. ("TRV III"). The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP III, TRV GP III LLC, Levin, Starr and Tepper disclaims beneficial ownership of these shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares. ( 2 )The Series A Preferred Stock is convertible into common stock on a 15.529-for-1 basis into the number of shares of common stock shown in Column 3 without payment of further consideration at the holder's election or upon closing of the initial public offering of the Issuer's common stock. The shares have no expiration date. ( 3 )The Series C Preferred Stock is convertible into common stock on a 12.6352-for-1 basis into the number of shares of common stock shown in Column 3 without payment of further consideration at the holder's election or upon closing of the initial public offering of the Issuer's common stock. The shares have no expiration date ( 4 )The Series D Preferred Stock is convertible into common stock on a 5.3-for-1 basis into the number of shares of common stock shown in Column 3 without payment of further consideration at the holder's election or upon closing of the initial public offering of the Issuer's common stock. The shares have no expiration date.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

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