The reason this noise works so well on a Construction site is because it mimics the noise from the discharge of pressurized air.<br>Air tools are common to the industry but not for the general public.<br>A Construction worker that hears this noise is going to react to it more so than Joe Public. It's effectiveness has to do with the fact that evolution has made us keenly aware of threats that may damage our senses and vision is the most important. Hearing an air tool discharge like that makes you instinctively asses the situation. If it is close to you, you might get your vision impaired. Either by debris, projectiles or the actual force of the air. You also shouldn't be able to habituate to it because the noise gives no indication for the size or nature of the threat. Is it a truck? Is it a guy filling a tire? Is it a nail gun shooting out brads towards your head? Don't know, better ID the noise and decide.