EXHIBIT NO. 10(c)

                      NOISE CANCELLATION TECHNOLOGIES, INC.


Verity Group PLC
Stonehill
Huntingdon  PE18 6ED

                                                             27 September 1997

Dear Sirs

This letter,  when countersigned by Verity Group PLC ("Verity") shall constitute
an agreement between Noise Cancellation  Technologies,  Inc. ("NCTI") and Verity
in relation to the common  stock  purchase  option  granted by NCTI in favour of
Verity dated 15 April, 1997 as executed by letter agreements dated  respectively
15 April 1997 and 17 April 1997 (the "NCTI Option") and the Registration  Rights
Agreement  between  Verity  and  NCTI  dated  as  at  15  April  1997  (the  "RR
Agreement").  All  capitalized  terms  used in this  Agreement  shall  bear  the
meanings given thereto in the NCTI Option unless the context otherwise requires.

1.      Amendment of NCTI Option

        Effective  the  date  hereof,  the  date on which  the  period  from the
        exercise  of  purchase   rights   begins  is  amended  from  "the  first
        anniversary  of the date hereof" to the date hereof  namely 27 September
        1997.

        Except as provided in this  Paragraph 1, all of the terms and conditions
        of the NCTI Option  (other than the said date) are hereby  ratified  and
        confirmed and remain in full force and effect.

2.      Amendment of RR Agreement

        Effective  the date hereof,  the  references  in the RR Agreement to the
        Option  shall be deemed to refer to the NCTI  Option as  amended by this
        letter.






Kindly  acknowledge your acceptance and agreement to the terms of this letter by
signing the  enclosed  copy of this letter and  returning  it to NCTI as soon as
possible.

Yours faithfully

NOISE CANCELLATION TECHNOLOGIES, INC

By:     /s/ MICHAEL J. PARRELLA
        Michael J Parrella, President

Verity Group PLC hereby accepts and agrees to the terms of this letter:

VERITY GROUP PLC

By:     /s/ FARAD AZIMA
        Farad Azima, Director