Yes, but only in a limited and specific sense. There are urban planter boxes and planter-based street furniture that are genuinely designed with noise control in mind, usually sold as “acoustic planters,” “noise-barrier planters,” or “soundproof planters.” These are not ordinary decorative boxes. They are hybrid products that combine a heavy planter wall, a substantial soil volume, dense evergreen planting, and sometimes internal sound-absorbing panels or a continuous barrier core. Their purpose is to reduce street noise while still providing greenery and street-level separation.
That said, a standard urban planter box is not a reliable noise barrier. Plants alone have a modest acoustic effect: leaves and branches can scatter and absorb some high-frequency sound, but they do little against low-frequency traffic rumble. To block street noise effectively, a planter system needs mass, density, height, continuity, and airtight joints. A row of small, isolated planters with gaps between them will not perform like a barrier. The noise will pass through gaps, under the boxes, over the top, and through lightweight sides.
A properly designed acoustic planter box works more like a low or mid-height noise barrier. The rigid planter walls add mass, the soil substrate adds further mass, and a dense hedge can absorb and diffuse some sound. Performance improves when the planter run is continuous, tall enough to break the line of sight between the road and the listener, sealed at the base and joints, and placed as close as possible to either the noise source or the receiver. Maintenance also matters: sparse or clipped-back plants reduce effectiveness, and wet versus dry soil can change performance slightly.
So the honest answer is: yes, acoustic planter boxes exist, but they are specialized products rather than ordinary planters. They can be a useful part of an urban noise-reduction strategy, especially where greenery, pedestrian separation, and street aesthetics are also priorities. However, they should not be expected to match a solid purpose-built noise barrier. For serious traffic-noise problems, they are best used as a supplement to proper barriers, speed reduction, road surfacing, and building insulation—not as a standalone fix.