Tire noise is mainly generated from the interaction between tire and pavement. Different combinations of tire and pavement usually generate noise of different levels and different frequencies. For the same tire and same pavement, the most important factor influencing the noise level is vehicle speed. To provide a detailed description of the effects of speed on the noise generation, the present study investigates the tire noise of nineteen tires of the same size but with different tread patterns. The study includes the standard reference test tire and four other normal patterned tires running on a nonporous asphalt pavement using an on-board sound intensity (OBSI) technique. This OBSI system also has an optical sensor to monitor vehicle speed and to perform order-tracking analysis. The field tests were conducted under different vehicle speed values (72-105 km/h; i.e., 45-65 mph). The effects of speed on the noise spectrum and on the overall noise level have been analyzed. In addition, using the optical sensor signal, the tire noise related to the tire tread pattern has been isolated from noises from all other sources. The effects of speed on the separated signals have also been investigated. It was found that increasing speed increases the frequencies and levels of tread-pattern–related noise component, while for the noise component not related to the tread pattern, increasing speed only increases its amplitude, not its frequency. In addition, the noise generated at the trailing edge of the contact patch is more sensitive to the speed than the one at the leading edge.