EXHIBIT 10.15

FINAL

REGISTRATION RIGHTS AGREEMENT

                This REGISTRATION RIGHTS AGREEMENT (the “Agreement”), made as of the
27th of April, 2005 (the
“Effective Date”), by and between American Technology Corporation, a Delaware Corporation
(“ATC” or the “Company”) on the one hand, and Greg O. Endsley, an individual
(“Endsley”), Douglas J. Paschall, an individual (“Paschall”) and Gordon &
Holmes LLP, a California limited liability partnership (“Gordon & Holmes”), on the
other hand, is made with reference to the following facts. Endsley, Paschall and Gordon & Holmes
are referred to collectively as the “Investors.”

R E C I T A L S

                A.
         ATC, Endsley, Paschall and certain
other parties entered into an Agreement of Settlement and Mutual Release on the Effective Date (the
“Settlement Agreement”), pursuant to which ATC agreed to issue the aggregate of Seventeen
Thousand Five Hundred (17,500) shares (the “Shares”) of ATC common stock, $0.00001 par
value (“Common Stock”), to be divided as follows: 8,750 shares to Endsley and 8,750 shares
to Paschall; provided that each of Endsley and Paschall instructed ATC to cause 3,500 shares of his
shares (for a total of 7,000 share) to be issued in the name of Gordon & Holmes as compensation
for legal fees incurred by the ESI Parties in the defense and prosecution of the claims described
in the Settlement Agreement The share certificates issued by ATC were therefore to be in the
following denominations:

	Endsley	5,250 shares
	 	 
	Paschall	5,250 shares
	 	 
	Gordon & Holmes	7,000 shares


                B.           ATC desires to grant the Investors
certain rights with respect to the registration of the Shares, subject to the conditions as set forth
herein.

A G R E E M E N T

                In consideration of the foregoing and the promises and covenants contained herein and other good and
valuable consideration the receipt of which is hereby acknowledged, the parties hereto agree as follows:

                1.            Definitions.  For the purposes of this Agreement:

                               1.1            “Registrable Securities” shall mean (i) the Shares and (ii) shares of Common Stock which
may be issued hereafter to the Investors with respect to the Shares in consequence of any additional
issuance, exchange or reclassification of the Common Stock, corporate reorganization or any other
form of recapitalization, consolidation or merger; provided, however, that Registrable Securities
shall not include any such securities sold by the Investors to the public either pursuant to a registration
statement or Rule 144 or sold in a private transaction.

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                               1.2            “Rule 144” shall mean Rule 144 promulgated under the Securities Act.

                               1.3            “Securities Act” shall mean the Securities Act of 1933, as amended.

                               1.4            “SEC” shall mean the Securities and Exchange Commission.

                               1.5            “Securities Exchange Act” shall mean the Securities Exchange Act of 1934, as amended.

                2.            Piggyback Registration.  If the Company shall at any time or times determine to file a registration statement under the Securities
Act for any shares of its Common Stock other than (i) registration statements on Forms S-4, S-8 or
any successor to such forms, (ii) another form not available for registering the Registrable Securities
for sale to the public or any registration statement including only securities issued pursuant to
a dividend reinvestment plan, or (iii) a registration statement in which the only securities to be
registered are securities issuable upon conversion of debt securities or other convertible securities
which are also being registered, the Company will notify the Investors in each case of such determination
at least ten (10) days prior to filing the registration statement and, upon the receipt of the Investors’
written request given within five (5) days after the Investors’ receipt of such notification,
the Company will use its best efforts to cause any of the Registrable Securities, as specified in
such request, to be registered under the Securities Act pursuant to such registration statement,
to the extent and under the condition that such registration is permissible under the Securities
Act and the rules and regulations thereunder. The Company shall have the right to terminate or withdraw
any registration initiated by it prior to the effectiveness of such registration whether or not any
of the Investors has elected to include securities in such registration. The Registration Expenses
of such withdrawn registration shall be borne by the Company in accordance with Section 4 hereof.

                3.            Underwriting.  In connection with any offering involving an underwriting of shares of the Company’s capital
stock, the Company shall not be required under Section 2 to include any of the Registrable Securities
of the Investors in such underwriting unless they accept the terms of the underwriting as agreed
upon between the Company and the underwriters selected by it, and then only in such quantity as the
underwriters determine in their sole discretion will not jeopardize the success of the offering by
the Company. 

                4.            Expenses.  The Company shall pay all expenses incurred in connection with any registration pursuant to this
Agreement; provided, that the Investors shall pay for (i) any brokerage or underwriting commissions
or discounts relating to Common Stock sold by the Investors, and (ii) fees of counsel to the Investors.

                5.            Information Supplied by the Investors.  In connection with any registration pursuant to this Agreement, the Investors shall furnish the Company
with such information or documents as the Company may reasonably request and as shall be required
by all applicable provisions of the Securities Act and the rules and regulations thereunder.

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                6.            Indemnification.  In the event any Registrable Securities are included in a registration statement under this Agreement:

                               6.1             To the extent permitted by law, the Company will indemnify and hold harmless the Investors, any underwriter
(as defined in the Securities Act) for the Investors and each person, if any, who controls the Investors
or underwriter within the meaning of the Securities Act or the Securities Exchange Act, against any
losses, claims, damages, or liabilities (joint or several) to which they may become subject under
the Securities Act, or the Securities Exchange Act, insofar as such losses, claims, damages, or liabilities
(or actions in respect thereof) arise out of or are based upon any of the following statements, omissions
or violations (collectively a “Violation”): (i) any untrue statement or alleged untrue
statement of a material fact contained in such registration statement, including any preliminary
prospectus or final prospectus contained therein or any amendments or supplements thereto; (ii) the
omission or alleged omission to state therein a material fact required to be stated therein, or necessary
to make the statements therein not misleading; or (iii) any violation or alleged violation by the
Company of the Securities Act, the Securities Exchange Act or any rule or regulation promulgated
under the Securities Act or the Securities Exchange Act; and the Company will pay to the Investors,
such underwriter or controlling person any legal or other expenses reasonably incurred by them in
connection with investigating or defending any such loss, claim, damage, liability, or action; provided,
however, that the indemnity agreement contained in this Section 6.1 shall not apply to amounts paid
in settlement of any such loss, claim, damage, liability, or action if such settlement is effected
without the consent of the Company (which consent shall not be unreasonably withheld), nor shall
the Company be liable in any such case for any such loss, claim, damage, liability, or action to
the extent that it arises out of or is based upon a Violation which occurs in reliance upon and in
conformity with written information furnished expressly for use in connection with such registration
by the Investors, or any such underwriter or controlling person of the Investors.

                               6.2             To the extent permitted by law, the Investors will indemnify and hold harmless the Company, each of
its directors, each of its officers who has signed the registration statement, each person, if any,
who controls the Company within the meaning of the Securities Act, any underwriter, any other person
or entity selling securities in such registration statement and any controlling person of any such
underwriter or other holder, against any losses, claims, damages, or liabilities (joint or several)
to which any of the foregoing persons may become subject, under the Securities Act or the Securities
Exchange Act, insofar as such losses, claims, damages, or liabilities (or actions in respect thereto)
arise out of or are based upon any Violation, in each case to the extent (and only to the extent)
that such Violation occurs in reliance upon and in conformity with written information furnished
by the Investors expressly for use in connection with such registration; and the Investors will pay
any legal or other expenses reasonably incurred by any person intended to be indemnified pursuant
to this Section 6.2, in connection with investigating or defending any such loss, claim, damage,
liability, or action; provided, however, that the indemnity agreement contained in this Section 6.2
shall not apply to amounts paid in settlement of any such loss, claim, damage, liability or action
if such settlement is effected without the consent of the Investors, which consent shall not be unreasonably
withheld; provided, that, in no event shall any indemnity under this Section 6.2 exceed the gross
proceeds from the offering received by the Investors.

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                               6.3             Promptly after receipt by an indemnified party under this Section 6 of notice of the commencement
of any action (including any governmental action), such indemnified party will, if a claim in respect
thereof is to be made against any indemnifying party under this Section 6, deliver to the indemnifying
party a written notice of the commencement thereof and the indemnifying party shall have the right
to participate in, and, to the extent the indemnifying party so desires, jointly with any other indemnifying
party similarly noticed, to assume the defense thereof with counsel mutually satisfactory to the
parties; provided, however, that an indemnified party (together with all other indemnified parties
which may be represented without conflict by one counsel) shall have the right to retain one separate
counsel, with the fees and expenses to be paid by the indemnifying party, if representation of such
indemnified party by the counsel retained by the indemnifying party would be inappropriate due to
actual or potential differing interests between such indemnified party and any other party represented
by such counsel in such proceeding. The failure to deliver written notice to the indemnifying party
within a reasonable time of the commencement of any such action, if prejudicial to its ability to
defend such action, shall relieve such indemnifying party of any liability to the indemnified party
under this Section 6, but the omission so to deliver written notice to the indemnifying party will
not relieve it of any liability that it may have to any indemnified party otherwise than under this Section 6.

                               6.4             If the indemnification provided for in this Section 6 is held by a court of competent jurisdiction
to be unavailable to an indemnified party with respect to any loss, liability, claim, damage, or
expense referred to therein, then the indemnifying party, in lieu of indemnifying such indemnified
party hereunder, shall contribute to the amount paid or payable by such indemnified party as a result
of such loss, liability, claim, damage, or expense in such proportion as is appropriate to reflect
the relative fault of the indemnifying party on the one hand and of the indemnified party on the
other in connection with the statements or omissions that resulted in such loss, liability, claim,
damage, or expense as well as any other relevant equitable considerations. The relative fault of
the indemnifying party and of the indemnified party shall be determined by reference to, among other
things, whether the untrue or alleged untrue statement of a material fact or the omission to state
a material fact relates to information supplied by the indemnifying party or by the indemnified party
and the parties’ relative intent, knowledge, access to information, and opportunity to correct
or prevent such statement or omission.

                               6.5             Notwithstanding the foregoing, to the extent that the provisions on indemnification and contribution
contained in the underwriting agreement entered into by a party to this Agreement in connection with
the underwritten public offering are in conflict with the foregoing provisions, the provisions in
the underwriting agreement shall control.

                               6.6             The obligations of the Company and the Investors under this Section 6 shall survive the completion
of any offering of Registrable Securities in a registration statement under this Agreement, and otherwise.
No indemnifying party, in the defense of any such claim or litigation, shall, except with the consent
of each indemnified party, consent to the entry of any judgment or enter into any settlement which
does not include as an unconditional term thereof the giving by the claimant or plaintiff to such
indemnified party of a release from a liability in respect to such claim or litigation.

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                7.            Termination of Registration Rights.  An Investor shall not be entitled to exercise any right provided for in this Agreement after the
first date on which all Registrable Securities then held by such Investor may immediately be sold
under Rule 144 during any 90-day period taking into consideration the volume restrictions specified
in Rule 144.

                8.            Non-Assignability.  This Agreement is personal to the Investors, and neither the Agreement nor any of the Investors’
rights or obligations hereunder may be assigned, pledged or encumbered by the Investors without
the prior written consent of ATC, which may be withheld in ATC’s sole discretion.

                9.            Miscellaneous.

                               9.1             Successors and Assigns.  Except as otherwise provided herein, the terms and conditions of this Agreement shall inure to the
benefit of and be binding upon the respective successors and assigns of the parties. Nothing in this
Agreement, express or implied, is intended to confer upon any party other than the parties hereto
or their respective successors and assigns any rights, remedies, obligations, or liabilities under
or by reason of this Agreement, except as expressly provided in this Agreement.

                               9.2             Governing Law.  This Agreement shall be governed by and construed under the laws of the State of California as applied
to agreements among California residents entered into and to be performed entirely within California.

                               9.3             Counterparts.  This Agreement may be executed in two or more counterparts, each of which shall be deemed an original,
but all of which together shall constitute one and the same instrument.

                               9.4             Titles and Subtitles.  The titles and subtitles used in this Agreement are used for convenience only and are not to be considered
in construing or interpreting this Agreement.

                                9.5             Notices.  Unless otherwise provided, any notice required or permitted under this Agreement shall be given in
writing and shall be deemed effectively given upon personal delivery to the party to be notified,
upon transmission by facsimile at the facsimile number indicated for such parties on the signature
page hereof, with confirmation of receipt, or upon deposit with the United States Post Office, by
registered or certified mail, postage prepaid and addressed to the party to be notified at the address
indicated for such party on the signature page hereof. Any party may change its address or facsimile
number by ten (10) days’ advance written notice to the other parties given in accordance herewith.

                                9.6             Expenses.  If any action at law or in equity is necessary to enforce or interpret the terms of this Agreement,
the prevailing party shall be entitled to reasonable attorneys’ fees, costs and necessary disbursements
in addition to any other relief to which such party may be entitled.

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                               9.7             Amendments and Waivers.  Any term of this Agreement may be amended and the observance of any term of this Agreement may be
waived (either generally, in a particular instance or prospectively), only with the written consent
of the Company and the Investors.

                               9.8             Severability.  If one or more provisions of this Agreement are held to be unenforceable under applicable law, such
provision shall be excluded from this Agreement and the balance of the Agreement shall be interpreted
as if such provision were so excluded and shall be enforceable in accordance with its terms.

                               9.9             No Delay of Registration.  No Investor shall have any right to obtain or seek an injunction restraining or otherwise delaying
any registration by the Company as the result of any controversy that might arise with respect to
the interpretation or implementation of this Agreement.

                               9.10           Entire Agreement.  This Agreement and the Settlement Agreement constitute the full and entire understanding and agreement
between the parties with regard to the subjects hereof and thereof.

[Signature Pages Follow]

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                IN WITNESS WHEREOF, the parties have executed this Agreement as of the date first written above.

	THE COMPANY:	THE INVESTORS:
	 	 
	American Technology Corporation, a 	Gordon & Holmes LLP, a California
	Delaware corporation	limited liability company 
	 	 
	By:  /s/  Bruce A. Gray                                         	By:  /s/  Frederic L. Gordon                           
	Name:  Bruce A. Gray                                          	Name:  Frederic L. Gordon                            
	Title:  Vice President, Government Group           	Title:  Partner                                                  
	 	 
	Address:	Address:
	13114 Evening Creek Drive South	223 W. Date Street
	San Diego, California 92128	San Diego, California 92101-3571
	Facsimile: 858.679.0545	 
	 	 
	 	Greg O. Endsley, an Individual
	 	 
	 	/s/  Greg O. Endsley                                       
	 	Greg O. Endsley
	 	 
	 	Address:
	 	25022 Footpath Ln.                                        
	 	Laguna Niguel, CA 92677                             
	 	Facsimile:  949.585.9866                               
	 	 
	 	 
	 	Douglas J. Paschall, an Individual
	 	 
	 	/s/  Douglas J. Paschall                                   
	 	Douglas J. Paschall
	 	 
	 	Address:
	 	5 Las Posadas                                                 
	 	Rancho Santa Margarita, CA                         
	 	Facsimile:  949.959.1252                               




[REGISTRATION RIGHTS AGREEMENT 

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