Supplement to Proxy Statement for the Special Meeting of Stockholders to Be Held on April 21, 2008

  
    
  
  
    
      SigmaTel, Inc. (NASDAQ: SGTL) provides the following information to 
      supplement and amend its Proxy Statement, dated February 29, 2008, 
      furnished to stockholders in connection with the solicitation of proxies 
      on behalf of the board of directors of SigmaTel for use at the Special 
      Meeting of Stockholders to be held on Monday, April 21, 2008, at 9:00 
      a.m. Central time at the offices of Vinson & Elkins L.L.P., The Terrace 
      7, 2801 Via Fortuna, Suite 100, Austin, Texas. The purposes of the 
      Special Meeting are as stated in the Notice of Special Meeting of 
      Stockholders, dated February 29, 2008, which accompanied the Proxy 
      Statement. This supplement should be read in conjunction with the Proxy 
      Statement.
    
    
      SigmaTel has retained Georgeson Inc. (“Georgeson”) 
      to assist in the solicitation of proxies for a base fee of $10,000, plus 
      expenses incurred in Georgeson’s performance, 
      and has agreed to indemnify Georgeson for liabilities and expenses, 
      including attorney’s fees, arising out of its 
      performance and not resulting from Georgeson’s 
      gross negligence or intentional misconduct, as determined by a court of 
      law pursuant to a final and nonappealable judgment.
    
    
      Additional Information about the Proposed Transaction and Where to 
      Find It
    
    
      SigmaTel has filed a definitive proxy statement and other documents 
      regarding the proposed transaction described in this press release with 
      the Securities and Exchange Commission. INVESTORS AND SECURITY HOLDERS 
      ARE URGED TO READ THE PROXY STATEMENT AND SUCH OTHER MATERIALS BECAUSE 
      THEY CONTAIN IMPORTANT INFORMATION ABOUT SIGMATEL AND THE PROPOSED 
      TRANSACTION. A definitive proxy statement was sent to security holders 
      of SigmaTel seeking their approval of the transaction. Investors and 
      security holders may obtain a free copy of the definitive proxy 
      statement and other documents filed by SigmaTel with the Securities and 
      Exchange Commission at the SEC’s web site at www.sec.gov. 
      The definitive proxy statement and other relevant documents may also be 
      obtained free of cost by directing a request to Martha Aviles at 
      512-744-9968.
    
    
      SigmaTel’s directors and executive officers 
      may be deemed, under Securities and Exchange Commission rules, to be 
      participants in the solicitation of proxies from the SigmaTel’s 
      stockholders in connection with the proposed transaction. Information 
      about SigmaTel’s directors and officers can be 
      found in SigmaTel’s Proxy Statements and 
      Annual Reports on Form 10-K filed with the SEC. Additional information 
      regarding the interests of those persons may be obtained by reading the 
      proxy statement and other documents regarding the proposed transaction.