APS Microphones and Speakers
Some APS require installation of microphones to monitor the ambient sound; this is part of the automatic sound adjustment feature. The microphones measure the sound levels to adjust the volume at the waiting location. If the microphone is mounted too far from the intersection, it will not adequately sample and adjust the volume levels, and the WALK indication is likely to be too quiet for a pedestrian at the curb to hear above the sound of traffic.
Speakers for APS may be pedhead-mounted or pushbutton-integrated. There are different issues to be considered, depending on the speaker location, though the majority of APS speakers are pushbutton integrated. Figures 6-33 and 6-34 indicate the different locations of speakers.
Some manufacturers also provide the option of having a speaker at the pedhead in addition to a speaker at the pushbutton location. This may be particularly useful where audible beaconing is installed, to focus the audible beaconing signal.
Sound dispersion from pushbutton-integrated speakers
While the speaker is usually built into the pushbutton-integrated device, different devices have slightly different speaker locations, and this affects the volume settings and the mounting of the device.
If possible, particularly in a location with audible beaconing, the devices should have speakers oriented toward the street, as well as the sidewalk and pedestrian waiting location. Beaconing is unlikely to be successful when provided by a device without speaker openings on the curb side. The addition of a pedhead-mounted speaker may need to be considered in a situation requiring beaconing. Some manufacturers sell optional add-on speakers or baffles to control direction of sound, when needed.
H-frame for pushbuttons
Figure 6-35. Example of H-frame pushbutton
An H-frame is used for mounting pushbuttons in some northwestern states, however, this device does not meet current MUTCD guidance which states that the face of the pushbutton should be parallel to the crosswalk to be used (MUTCD 2009, Section 4E.08, P4). Some APS devices will not work properly when mounted in this configuration. The type of device and location of speaker components should be considered before ordering. The arrow of the APS is often part of the pushbutton and may not be oriented properly in the H-frame. In addition, the design of the frame makes it difficult to hear the sound of the locator tone from both the approach direction and the crossing direction.
It can be helpful for pedestrians who are blind to hear the locator tone as they complete their street crossings (the WALK indication is seldom still sounding by that time). In this type of mounting, the pushbutton locator tone is not audible from the street because the speaker is aimed back toward the building line.
If two pushbutton-integrated APS in H-frames are mounted on a single pole, they will provide ambiguous WALK indications because the APS closest to each crosswalk will be indicating the perpendicular crosswalk, not the closest crosswalk.
The speaker for the locator tone in Figure 6-36 is oriented toward the building line, rather than toward the street (in the location shown in the photo, the WALK indication comes from an overhead speaker). One of the arrows points toward the pole and the other device, as well as toward the street, but it would be hard to use the arrow for direction when standing on the sidewalk side of the pole.
Illustrations of ideal, acceptable, and unacceptable locations of pushbutton-integrated devices and speakers
The drawings on the following pages illustrate proper and improper positioning of pushbutton-integrated devices and speakers. In the following captions, "retrofit" refers to the installation of APS at existing intersections. A retrofit might involve some constraints on the installation process, such as the inability to have two separate poles on a single corner. It is assumed that the sidewalk beside the pushbutton is firm and level as required by the MUTCD and Proposed PROWAG.
Figure 6-37. Ideal placement for pushbutton-integrated APS
Figure 6-38. Acceptable placement for pushbutton-integrated APS
Figure 6-39. Acceptable placement for pushbutton-integrated APS, only when installing in a retrofit situation on an existing pole (if APS cannot be separated, there will need to be a speech pushbutton information message and speech WALK message to prevent ambiguity)
Figure 6-40. Acceptable placement for pushbutton-integrated APS, only when installing in a retrofit situation on an existing pole (if APS cannot be separated, there will need to be a speech pushbutton information message and WALK message to prevent ambiguity)
Figure 6-41. Unacceptable placement for APS speakers (the positioning provides ambiguous information)
Figure 6-42. Unacceptable placement for pushbuttons and tactile arrows of APS (not reachable from level all-weather surface)
Sound from pedhead-mounted speakers
Figure 6-43. This photo shows a view from below of a speaker attached to the pedhead support and aimed straight down
Figure 6-44. The pedhead and APS speaker for the north/south crosswalk is located over the pushbutton for the east/west crosswalk
The sound from pedhead-mounted speakers is not very useful for providing guidance about the location of the opposite curb. Unless audible beaconing is required, speakers should be aimed down toward the pedestrian waiting location.
Speakers may be aimed toward the center of the street at crosswalks where beaconing is needed. For pedhead-mounted speakers, sound will travel farther the more nearly horizontal the radiation pattern of the speaker is.
- Where beaconing is not needed, speakers should be pointed down toward the location of pedestrians waiting to cross the associated crosswalk, which will also minimize noise in neighborhoods.
- Where beaconing is needed, the speaker must be pointed toward the middle of the associated crosswalk (centerline of the road). A side effect of this design is that the APS will produce more noise in the neighborhood.
While the direction of the speaker does make a difference, it is common for overhead speakers that are attached to pedheads to provide ambiguous information. Figure 6-44 illustrates such a speaker and pedhead placement. In both cases, the mounting is problematic because the speakers are mounted on a pedhead that is not over the departure location of the crosswalk they signal.
The speaker in Figure 6-44 is located on the side of the pedhead and sounds for the north/south crosswalk. It is situated directly over the waiting area to cross to the east and some distance from the north/south departure point. This configuration can be very confusing to pedestrians who are blind.
Acceptable and Unacceptable Locations of pedhead-mounted speakers
The drawings on the following pages illustrate proper and improper positioning of pedhead-mounted devices and speakers.
Figure 6-45. Possible placement for APS speakers mounted on the pedestrian signal head at pretimed signals; no beaconing
Figure 6-46. Recommended placement for pedhead-mounted speakers where beaconing is needed
Figure 6-47. Possibly acceptable placement for pedhead-mounted APS on the outside of the pedheads. Provide as much separation as possible.
Figure 6-48. Possibly acceptable placement for pedhead-mounted APS using mast arms to provide additional separation
Figure 6-49. Unacceptable placement for pedhead-mounted speakers, regardless of how speakers are aimed
Figure 6-50. These APS speaker placements are unacceptable, regardless of how speakers are aimed
Figure 6-51. These APS placements are unacceptable, regardless of how speakers are aimed
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