SIXTH AMENDMENT TO LOAN AGREEMENT

            SIXTH AMENDMENT TO LOAN AGREEMENT

THIS SIXTH AMENDMENT TO LOAN AGREEMENT (this "Amendment"), dated as of April 30, 2009, is between CONCORD TECHNOLOGIES, LP, a Texas limited partnership ("Concord"), GEOSPACE ENGINEERING RESOURCES INTERNATIONAL, LP, a Texas limited partnership ("Engineering"), GEOSPACE TECHNOLOGIES, LP, a Texas limited partnership ("Geospace"), OYO INSTRUMENTS, LP, a Texas limited partnership ("Instruments"), and OYOG OPERATIONS, LP, a Texas limited partnership ("Operations", and together with Concord, Engineering, Geospace and Instruments, the "Borrowers"), jointly and severally, and REGIONS BANK (F/K/A UNION PLANTERS BANK, N.A.) ("Lender").

            RECITALS:

            Borrowers and Lender entered into that certain Loan Agreement dated as of November 22, 2004, as amended by that certain First Amendment to Loan Agreement dated as of September 19, 2005, Second Amendment to Loan Agreement dated as of June 16, 2006, Third Amendment to Loan Agreement dated as of January 10, 2007, Fourth Amendment to Loan Agreement dated as of October 12, 2007, and Fifth Amendment to Loan Agreement dated as of March 12, 2008 (as amended, the "Agreement").

            Pursuant to the Agreement, (i) OYO Geospace Corporation, a Delaware corporation ("Parent"), OYOG, LLC, a Delaware limited liability company ("General Partner"), and OYOG Limited Partner, LLC, a Texas limited liability company ("Limited Partner"), executed those certain Guaranty Agreements each dated as of January 10, 2007 (collectively, the "2007 Guaranties"), and (ii) Geospace Finance Corp., a Texas corporation ("GFC" and together with Parent, General Partner and Limited Partner, the "Guarantors"), executed that certain Guaranty Agreement dated as of March 12, 2008 (together with the 2007 Guaranties, the "Guaranty Agreements") pursuant to which Guarantors guaranteed to Lender the payment and performance of the Obligations (as defined in the Agreement).

            Borrowers and Lender now desire to amend the Agreement as herein set forth.

NOW, THEREFORE, in consideration of the premises herein contained and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto agree as follows:

            ARTICLE

            Definitions

Section          Definitions . Capitalized terms used in this Amendment, to the extent not otherwise defined herein, shall have the meanings given to such terms in the Agreement, as amended hereby.

            ARTICLE

            Amendments

Section          Amendment to Certain Definitions . Effective as of date hereof, the definition of each of the following terms contained in Section 1.1 of the Agreement is amended to read in its respective entirety as follows:

" Applicable Margin " means, for the Levels described below, the percentage amounts set forth below.

Level I applies when the Cash Flow Leverage Ratio is equal to or greater than 2.00 to 1.00.

Level II applies when the Cash Flow Leverage Ratio is equal to or greater than 1.50 to 1.00 but less than 2.00 to 1.00.

Level III applies when the Cash Flow Leverage Ratio is equal to or greater than1.25 to 1.00 but less than 1.50 to 1.00.

Level IV applies when the Cash Flow Leverage Ratio is equal to or greater than 1.00 to 1.00 but less than 1.25 to 1.00.

Level V applies when the Cash Flow Leverage Ratio is less than 1.00 to 1.00.

The applicable Level shall be adjusted, to the extent applicable, effective sixty (60) days after the end of each quarter (or, in the case of any change reflected by the audited financial statements delivered pursuant to Section 7.1(a), one hundred twenty (120) days after the end of any fiscal year) based on the Cash Flow Leverage Ratio tested for the period ending on the last day of such quarter or such fiscal year, as applicable; provided that if Borrowers fail to deliver the financial statements required by Section 7.1(a) or (b), as applicable, or the related No Default Certificate required by Section 7.1(c) by the sixtieth (60th) day after the end of any quarter (or, if applicable, the one hundred twentieth (120 ^th ) day after the end of any fiscal year) Level I shall apply until such financial statements and No Default Certificate are delivered.

" Applicable Rate " means the sum of the LIBOR Rate plus the LIBOR Margin from time to time in effect.

" Default Rate " means a per annum rate of interest equal to the lesser of (a) the sum of the Applicable Rate then in effect from day to day plus two percent (2.0%), but not less than seven percent (7.0%) per annum, or (b) the Maximum Rate.

" Funded Debt " means, at any time, for Parent and its Subsidiaries, on a consolidated basis (and without duplication), all Debt for borrowed money which bears interest, whether or not evidenced by bonds, debentures, notes or similar instruments, including the Note, and all other Debt (including Capital Lease Obligations), which bears interest.

" LIBOR Rate " means, as of any day, the rate per annum offered for Dollar deposits in an amount comparable to the principal amount of the outstanding Advances for a period of thirty (30) days as of 11:00 a.m. City of London, England time two (2) London Business Days prior to the first (1 ^st ) day of the month in which such date occurs as published in the Wall Street Journal (or any successor publication if the Wall Street Journal is no longer published) in the "Money Rates" Section (or such successor section); provided that for the period from the initial Advance until the last day of the month in which such Advance occurs, such rate shall be determined as of two (2) Business Days prior to such initial Advance. If a range of such rate is published "LIBOR Rate" shall mean the highest rate in such published range. If such rate is not available in the Wall Street Journal, then such offered rate shall be otherwise independently determined by Lender from an alternate, substantially similar independent source available to Lender and recognized in the banking industry. Except as provided above for the initial Advance, the LIBOR Rate shall be set on the first (1 ^st ) day of each month as provided above and shall remain in effect until reset on the first (1 ^st ) day of the following month. Any Advances outstanding on the effective date of the Sixth Amendment to Loan Agreement dated as of April 30, 2009 (the "Effective Date") shall be treated as initial Advances made on the Effective Date (with no breakage penalty applicable thereto on the Effective Date).

" Termination Date " means 11:00 a.m., Houston, Texas time on April 30, 2011, or such earlier date on which the Commitment terminates as provided in this Agreement.

            the following definitions shall be added to Section 1.1 of the Agreement in proper alphabetical order:

" Cash Flow Leverage Ratio " means for Parent and its Subsidiaries, on a consolidated basis, as of any date of determination, the ratio of (a) the difference of (i) Funded Debt as of such date, minus (ii) Real Estate Debt as of such date, to (b) EBITDA for the period ended as of such date minus $1,000,000.00.

" Fixed Charge Coverage Ratio " means for Parent and its Subsidiaries, on a consolidated basis, as of any date of determination, the ratio of (a) EBITDA for the period ended as of such date, to (b) the sum of (i) Interest Expense for the period ended as of such date, plus (ii) Income Tax Expense for the period ended as of such date, plus (iii) Current Maturities of Long Term Debt as of such date, plus (iv) Maintenance Capital Expenditures for the period ended as of such date.

" LIBOR Margin " has the meaning given to such term in the definition of the term "Applicable Margin".

" Maintenance Capital Expenditures " means, for Parent and its Subsidiaries, the minimum amount of capital expenditures, as estimated or forecasted by Parent management, necessary to keep Parent and its Subsidiaries operating at current levels.

" Real Estate Debt " means all Debt secured by a Lien on the real property of Parent or its Subsidiaries.

            the definition of each of the following terms shall be deleted from Section 1.1 of the Agreement:

"Accounts"

"Asset Coverage Ratio"

"Continue", "Continuation" and "Continued"

"Convert", "Conversion" and "Converted"

"Debt Service Coverage Ratio"

"Distribution"

"Eligible Notes"

"Interest Period"

"Inventory"

"LIBOR Advances"

"Net Fixed Assets"

"Notes Receivable"

"Prime Rate"

"Prime Rate Advances"

"Ratio of Total Liabilities to Tangible Net Worth"

"Reserve Requirement"

"Total Liabilities"

"Type"

Section          Amendment to Sections 2.3 and 2.5 . Effective as of the date hereof, Sections 2.3 and 2.5 of the Agreement are amended to read in their entirety as follows:

Section 2.3.  Repayment of Principal and Interest; Extension . (a) Accrued and unpaid interest on the Advances (and, therefore, the Note) shall be due and payable on the last day of each month, commencing May 31, 2009.

(b)      The principal of the Advances, plus accrued and unpaid interest, shall be due and payable on the Termination Date.

(c)       Prior to the Termination Date, Lender will review such matters as it may deem appropriate in its sole discretion and may, in its sole and absolute discretion, determine whether to extend the Termination Date.

Section 2.5.  Requests for Advances . (a) As long as the provisions of the Autopay Agreement related to automatic advances are in effect, Advances may be made as provided in the Autopay Agreement, and Bor