Sonifying Traffic Data

Listening to our field recordings, we immediately heard how much the sound of traffic dominated our Boyle Heights site. We may assume that traffic is a drone–an unchanging, fixed amount of noise in our environment. But listening to our recordings, the sound of each vehicle approaching, passing, and departing had its own specific shape. The sound of many vehicles passing contained patterns that were periodic and reminded me of musical rhythm. To understand these underlying “rhythms,” I extracted data from our recordings about the length of vehicles passing, as well as their maximum amplitude (see this blog post). I then sonified the data in a variety of ways. The goal is to use sound to further articulate patterns in the sonic data. Sonification can make audible the rhythm of traffic because sound is a time-based medium. I also hope musicians, particularly the ones from the Boyle Heights neighborhood, might be inspired to take this data and make their own music with it, playing with the city’s sounds in their music.

Sonification with Filtered Noise

With SuperCollider, an open source musical programming language, I used a very simple synthesizer, made up of filtered noise, to sonifiy the data. The duration of passing vehicles controls the length of each sound, and vehicle loudness controls the maximum volume.

Sonification with MIDI

Also using SuperCollider, I wrote a script that generates MIDI files, where the  duration of passing vehicles is set to note length and loudness to volume (MIDI velocity to be technical). MIDI is a useful format because it is used in nearly all computer music programs. It can also be sped up or slowed down, and “quantized,” which means that each MIDI note can be snapped to a particular beat. The first example speeds up the data 10x and quantizes it, using a bass synth sound. Wendy played with the MIDI data and sped it up 8x. She used an Arp sample in Ableton Live to sonify the periodicity data resulting in the following track. If you’re interested in the SuperCollider source code and our data set, please contact me: @stevenTkemper or stevenTkemper [at] gmail


Here is the un-quantized original MIDI file. Please feel free to download, use, play with it. Let us know what you make with it! Periodicity of Traffic in Boyle Heights (MIDI)

Steven Kemper is Assistant Professor of Music Technology and Composition at the Mason Gross School of the Arts at Rutgers, The State University of New Jersey

A sound walk through the changing street economy of Boyle Heights

A repost from the our 3-part blog series that we published on Colab Radio through a collaboration with MIT Community Innovators Lab. This final post features Wendy’s ethnographic observations and sound walk of Boyle Heights. You can also read post #1 and #2.

Mariachi Plaza

Mariachi musicians performing at Mariachi Plaza in Los Angeles. Photo Credit: Flickr/::Alejandro::

It’s a sunny Saturday afternoon and Shmueli Gonzales is taking me through Boyle Heights, the neighborhood in which he grew up and now works closely with as an organizer. Staying within the three-block radius around the Soto Station on E. Cesar Chavez Boulevard we engage with the live sounds and sights all around us on our walk. Shmueli shares community stories and I follow up with questions about their social, political, and economic significance. Together we are participating in a soundwalk, an in situ interview about and through sound that allows me to explore the meaning of neighborhood vibrancy with a community expert.

In the final post of this blog series about LA Listens, a multidisciplinary exploration of neighborhood sounds in Los Angeles, I take an ethnographic approach to delve deeper into how sound mediates the social and economic relations of Boyle Heights. Sounds communicate not only who is saying what, but also how something is being said. In some instances, the intent and power relations of a social interaction can be heard through a close examination of the volume, tone, and technological vehicle through which an expression is delivered. In other instances, sound is an incidental byproduct of an activity. In both cases sound can reveal hidden social dynamics that go beyond what is seemingly sanctioned within and outside of a community.

Mariachis: Listening through assumptions and vehicular traffic

One of the most striking moments in the field recording that we captured at the corner of E Cesar Chavez and Chicago is a mariachi playing an upright bass. Standing under an awning outside of a restaurant, a mariachi musician banters with his colleagues while casually playing the notes of a song’s bassline. The sound of this walking bass is sometimes masked by vehicular traffic sounds. You can hear that the mariachi bass interacts with the ambient sounds of the street, remixing the radio projected by storefront stereo systems, potholes clicking, passing traffic sounds including squeaky brakes on a bus and the occasional ice cream truck playing folk and nursery rhymes over loudspeakers — all into a pleasant ensemble of music and sounds. If you listen more closely, you can even hear the strings hitting the fingerboard of the upright bass, adding to the rhythmic feel of this “street remix.”

Please use headphones to listen to this recording:

Located close to downtown, Boyle Heights is currently facing significant development pressure. Metropolitan Transportation Authority officials and developers are proposing to build a transit center and an affordable housing complex at Mariachi Plaza, just five blocks southwest of our recording site. The community is expressing concerns that the development will threaten the local economy, and in turn, the mariachis’ livelihood. According to Shmueli, the change in uses will be accompanied by a change in name– from Mariachi Plaza to Plaza del Mariachi. To the residents and members of the community, the proposed name change signifies the loss of the mariachis’ cultural ownership over the space as a site for both their artistic and business practice. Shmueli explained, “While the new [name would be] grammatically correct in Spanish, it doesn’t ring with Chicanos because it takes the mariachis from being first in the name to being last in the name…In our minds the mariachis are supposed to come first when we consider the space.”

The development proposals elicit a tension around the role of mariachis in the local economy. For the musicians, Mariachi Plaza is an active place of music commerce. But the developers and the city imagine the space as a backdrop for hip downtown dwelling with a historic cultural flair. Their plans do not consider how the mariachi musicians will continue to do their business. Furthermore, in their response to the developers and transit officials, community members talk about mariachi as a part of the local “culture” that calls for “preservation” efforts. The language of preservation implies that mariachi is a part of the historic landscape of the neighborhood, a cultural relic of the past with needs for preservation. Both of these views overlook the mariachis’ dynamic contribution to the public sphere. Mariachis as active performing professionals have played critical part of the local economy since the 1950s (Lamadrid 2013).

The silencing of mariachis’ voices in discussions about development and gentrification poses a stark contrast with their lively hustling and bustling in the neighborhood’s soundscape. Mariachi is a living itinerant performance practice that has thrived through successive social and economic changes. Their ambulatory business model and partnerships with local restaurants and businesses require entrepreneurial thinking and business ingenuity. The assumption of mariachis’ role as passive in the local economy excludes the consideration of the musicians’ material reality as professional musicians. Listening more closely, through the vehicular traffic sound wall and urban planners and developers’ assumptions about the musicians’ role in the local economy, we can better understand the following: how the mariachis articulate their life through songs about love and hope; and how the musicians maintain their artistic vitality and business viability as the neighborhood undergoes economic changes.

A Volume War

Across the street from where Shmueli and I walk, I see a couple of mariachi musicians, wearing their silver studded costumes, dancing to the techno music blasting from the power speakers in front of a Cricket Wireless storefront. Swaying to the electronic beats, they seem to be having a good time. A laptop DJ plays MP3s through a set of power speakers at a volume that almost entirely drowns out the sounds coming the other parts of this street intersection. Meanwhile, on my side of the street, in front of a second hand store, a USB propelled karaoke system blares ranchera and norteño, recorded sounds of regional Mexican music. Shmueli tells me that businesses in Boyle Heights use music and sounds to attract customers.

LAListens USB SoundSystem Boyle Heights sidewalk

Sounds play a central role in the entrepreneurial practices of the local businesses. This kind of “volume war,” where Cricket Wireless, a national telecommunication cell phone service provider, pumps out sounds that are substantially louder than local merchants, exemplifies the encroaching of big businesses in a neighborhood with an economy primarily supported by local and small businesses. Listening to the differences in amplitude and performance style (a laptop DJ with powerful sound speakers hired by Cricket), we can begin to hear the emerging presence of businesses that are out of scale with the current local economy.

Sound and space are inextricably tied to one another. In a public space, sounds can travel across various layers of the street — from interior to the exterior. Music from a storefront sound system, vendors hollering for business while pushing a cart of strawberries over the cracks in the sidewalk, Christian evangelist disseminating religious messages over a megaphone, mother and daughter conversing with a vendor selling flower bouquets in buckets on a truck bed, passing cars blaring the sounds of a button accordion in a norteño song on the radio. These are just some of the permeable layers of sounds that reverberate between the storefront, sidewalk, and road– the infrastructural tiers that make up public space. Sounds can move across the hard architectural and street structures, and travel from private to public, as people gather, trade, and socialize. In the image below, I have annotated the permeable sound layers of a street.

LAListens Boyle Heights Public Sound Layers Annotated

Whose turf is it anyway?

Some sounds are localized while others render themselves as an immersive, over-encompassing experience. Unlike localized sound sources like the sidewalk karaoke system, the LAPD helicopters frequent neighborhoods of Los Angeles while projecting an immersive sound that envelopes the space completely. Shumeli tells me that residents of Boyle Heights refer to them as “ghetto birds.” The loud, low-frequency sounds from these helicopters mask sounds from other localized sources. Some residents consider these helicopters as a bad omen. Others experience feelings of comfort and nostalgia because they associate helicopter sounds with home. One common local response is to first point at the aircraft and then inquire about the reason for this particular instance of surveillance on social media. For residents, the sheer presence of these out-of-the-human-scale machine sounds, activates an impulse to interrogate one’s surrounding with questions related to community and safety.

Use headphones to listen to this recording:

Brandon LaBelle notes that “Sound creates a relational geography that is most often emotional, contentious, fluid, and which stimulates a form of knowledge that moves in and out of the body” (2010 272-277). The understanding of helicopters’ sonic impact on social life in a neighborhood needs to be nuanced through both considerations of the physical parameters and the varied emotional responses it generates from residents. Sounds can territorialize a space but whose space is being occupied by whom (and how these boundaries are defined and enforced) is a social question. Listening to the sonic dynamics of a place may help us understand the social and political struggle of various entities at play: residents, government, police, shoppers, vendors, planners, developers, businesses, etc.

Finally, sense-based engagement can cultivate empathy and connection. My soundwalk with Shmueli got me to listen from his perspective as a community member. Good listening practices can lead to inquiry that sparks discussions. Beyond jumping into conclusions about the meaning and impact of what we hear, we should ask, who is vocalizing/sounding, what are they saying, how are they saying it, why are they saying it? Urban planners should listen more carefully to what constitutes neighborhood vibrancy. As planners are designing to create neighborhood-level change, ask yourself if you are: 1) hearing the sounds or voices that dominate and how they dominate a space; 2) and you are listening through the layers of sounds and assumptions to identify who and what is out of the current discourse about change.

As Shmueli and I turn away from E Cesar Chavez Avenue to circle around the neighborhood back to the Metro station, I hear sporadic rattling sounds of objects loosely positioned on the back of a metal collector truck, construction workers blasting and singing along to ranchera ballads while renovating residential properties, all against the constant humming of high-speed traffic on Interstate Highway 5. These sounds tell me a bit about the livelihood of the informal metal recycling business, the recent economic development in the neighborhood that threatens displacement for some residents, and the memory of the multiethnic neighborhoods demolished by highway construction in the 1950s. Listening to the sounds and the stories they provide, I continue to learn about Boyle Heights.

Works Cited

LaBelle, Brandon. 2010. Acoustic Territories: Sound Culture and Everyday Life. New York: Continuum.

Lamadrid, Enrique, R. 2013. “A Paen to Santa Cecilia, Her Fiesta, and Her Mariachis,” Hotel Mariachi: Urban Space and Cultural Heritage in Los Angeles. Albuquerque, N.M.: University of New Mexico Press.

Post by Wendy Hsum, an ethnomusicologist and sound ethnographer working on public humanities and civic design projects.

Listening to the Streets: What sounds do vehicular traffic mask?

A repost from the our 3-part blog series that we published on Colab Radio through a collaboration with MIT Community Innovators Lab. This post #2 features Steven’s investigation of our sonic data. You can read post #1.

Boyle Heights Mural

Boyle Heights Mural. Photo Credit: jondoeforty1.

Standing at the intersection between East Cesar E Chavez Avenue and Chicago Street in Boyle Heights, I can hear many sounds unique to this neighborhood. Mariachi musicians playing bass on the street, recorded music coming from stores, and the sounds of people talking as they walk along the sidewalk. By far the most dominant sound is that of the passing vehicular traffic. Sounds of passing vehicles provide a semi-regular, underlying rhythm to the overall aural experience of the place. There are moments of dense vehicular activity and moments in which traffic ebbs and flows. In this second post of our blog series on LA Listens, I discuss the rhythm of vehicular traffic sounds by examining the following excerpt from our 19-minute field recording of Boyle Heights:

Measuring the Sound of Passing Vehicles

By understanding the periodicity of traffic noise, we can uncover the rhythmic aspects of the sonic experiences of this location. In order to identify the sonic qualities of passing vehicles, I’ve taken a two-pronged approach of listening to the sound and visualizing it in a sonogram (sound spectrogram)—a plot of the frequency information of a sound over time. I’ve used the Raven Interactive Sound Analysis software developed by the Cornell Lab of Ornithology Bioacoustics Research, to help identify and analyze the changing patterns in vehicular traffic sounds.

Sonogram of 2 minute sampleSonogram of our 2 minute sample

Sonogram of a Vehicle Passing

Sonogram of a Vehicle Passing

In the same way that light is made up of component colors (wavelengths) of the visible spectrum, which can be viewed individually by using a prism, sound is made up of combinations of individual frequency components ranging from low to high. Like a prism, a sonogram allows us to see all of the individual components that make a sound, representing three dimensions of data: time, individual frequency components of sound, and the loudness (power) of those frequency components. The horizontal axis represents time (in seconds), the vertical axis represents the frequency range of the sound (in kHz), and the colors represent the loudness of each frequency component. For reference, this site from Columbia University provides a more detailed explanation of sound and loudness.

Sounds of a vehicle driving generally consist of the sound from the engine, tires on the pavement, and wind. This group of sounds take up virtually the entire frequency spectrum, and fades in and out as the vehicle passes the recording position. Louder frequency components are represented by a brighter color, i.e. neon green in the above example. I extracted the above sonogram from our field recording. The vertical line in neon green indicates a moment when a vehicle passes our recording site. The visual form of the sounds of individual passing vehicles becomes identifiable after listening to these sounds while looking at the sonogram.

30 events of passing vehicles detected in the recording30 events of passing vehicles were detected in the recording

Raven provides information about each passing vehicle’s timing and duration. I used Raven to isolate passing vehicles as sonic events. Analysis of the recording shows 30 instances of passing vehicles. The unit of comparison indicated in the chart below is a single sound event, the duration of either a single passing vehicle, or multiple vehicles without a discernable break between them.

Sound of Passing Vehicles Time (seconds)
Average duration      2.2
Median duration      1.84
Minimum duration      .59
Maximum duration      5.01
Total time of vehicle sounds      65.9
Percentage total time vehicle sounds      55


This analysis nuances our understanding of the sensory experience of the streets. It tells us how much our aural experience is dominated by sounds of vehicular traffic. In this 2-minute recording, over half of our time (55%) is spent listening to passing cars! Additionally, the duration value of passing vehicles can provide a point of reference for the rate at which the vehicular traffic flows. This information may be useful for urban planners and organizers to understand the impact of street infrastructures like traffic signals on pedestrians and cyclists especially as they consider design elements related to safety, flow, and street intersections.

Speculating a Vehicle-free Neighborhood

Knowing that our aural experience is dominated by vehicular traffic sounds, I decided to make a vehicle-free version of our 19-minute field recording by removing all moments that include vehicular traffic sounds. For the sake of continuity, I left out moments between vehicles that were shorter than 3 seconds. The resulting recording is only 2:37 long, which demonstrates just how prevalent vehicular noise is in the neighborhood.

Through this recording, we can imagine a sonic landscape of the streets in Boyle Heights absent of the sounds of cars, buses, trucks, and motorcycles constantly passing by. (Air traffic, including planes and helicopters has not been removed). This virtual soundscape provides a model for an augmented reality app that I would eventually like to create–one that removes the sound of traffic in real time.

Preview of Blog Post #3

In the next and final post of our blog post series, Wendy will take us through a soundwalk with a community expert through Boyle Heights, to explore the political and economic significance of neighborhoods sounds in social contexts.

Post by Steven Kemper, a composer of acoustic and electroacoustic music and a music technologist who focuses on interactive technologies and robotics.

Investigating Vibrancy through Listening to Urban Sounds

This is a repost from the our 3-part blog series that we published on Colab Radio through a collaboration with MIT Community Innovators Lab. Part 1 of the series introduces LA Listens to the Colab Radio audience, urban planners and organizers with an interest to “deepen civic engagement, improve community practice, inform policy, mobilize community assets, and generate shared wealth.”

mariachi plaza/boyle heights

Mariachi Plaza in Boyle Heights LA. Photo Credit: Flickr/Paul Narvaez

How Three Sound Scholars Listen Differently

Vibrancy is often talked about in urban planning and development discussions. It is sometimes described as a desirable quality that has waned and is in need of restoration. Other times, it is castigated as being too closely associated with upper middle class urban elites’ consumptive appetite for inner city lifestyles. As three sound scholars who are not urban planners, these discussions lead us to wonder if there are distinctive sonic qualities of what is perceived as “vibrant.” If so, what are they? To explore this question, the three of us, a sound ethnographer, acoustic ecologist and a composer/music technologist, have formed LA Listens. In addition to this question of vibrancy, we’ve come together over a shared interest in urban sounds and Los Angeles. Coming from distinct disciplinary interests, we each have particular questions that we are interested in.

Jessica is curious about how the characteristics of the urban soundscape in Los Angeles affect the way we interact with our environment and each other. Steven is interested in understanding the sonic qualities of urban sounds while exploring the musical qualities of places. For example, he is exploring the idea that repeating events can be seen as rhythm on a macro-level time scale. Finally, Wendy has questions about how people make sense of urban sounds culturally and socially, particularly in light of the politics related to urban development and placemaking.

While our questions diverge in terms of perspective, a cross cutting underlying interest for all of us is the effects of urban sounds on people. To that end, LA Listens takes an experimental analytic approach to listen to the interrelationships between the sensory, social, and ecological aspects of streets in Los Angeles. Sounds permeate through spaces in the form of layers. Through this structure, sounds form the identity and construct the experience of a place. Through engaging with the experiential and data dimensions of place-based sensory traits we can analyze the permeable layers of LA’s public acoustic territory (Atkinsons 2007; LaBelle 2010).

Our research goals extend into the civic and creative realms. We intend to offer sensory data as resources for city planners and community organizers to draw upon when engaging in policy and other conversations. We also want to spark a creative dialogue, providing artists with access to our data to co-produce reflexive interpretations of the city’s sounds.

A Multimodal Approach to Studying Urban Sounds

As sound scholars, we agreed that location recordings offer a nuanced and sense-based understanding of the human experience of place and space. To brainstorm locations in Los Angeles in which to scrutinize the meanings of “vibrancy”, we came up with a two-pronged approach touching on both data and policy related to environmental sounds in Los Angeles. First, we looked for relevant data published through the City’s portal. Curious about the role of vehicular sounds in the urban landscape, we mapped the city’s collision data from this year in order to identify busy and dangerous street intersections.


Additionally, we wanted our project to speak to the city’s current urban development programming and policy, so we selected street intersections within the corridors that have been chosen as a part of the LA Mayor’s Great Streets program. We then walked around these street corridors and intersections, listening closely to and taking note of the sonic and social properties of the changing sound environment. This ambulatory listening practice is typically referred to as a sound walk (Tausig 2011).

LA Listens- Steve sound walk

Steve recording sounds

After we identified a single spot, rich in layers of static and dynamic sounds generated by a constellation of natural, human-made, and machine-made sources, we set up our recording gear. We stood at intersections in Highland Park and Boyle Heights and captured 10-20 minute neighborhood-level field recordings. We also recorded a busy intersection in Little Tokyo in downtown Los Angeles.

We intend for this project to reject the siloed disciplinary approaches to researching sound by experimenting with research modalities and tools from sound-specific disciplines across the humanities, sciences, and the arts. In doing so, we hope to offer urban planners fodder for integrating sound into their planning processes.

In approaching this work from different disciplines, we have also learned the value of a collaborative design process and the value of establishing a complex research methodology through negotiation.

In our next blog post, we will delve into how we analyze our location recordings through sharing some of our individual and collective thoughts on our preliminary findings from the East Los Angeles neighborhood of Boyle Heights. Stay tuned!

Works Cited

Atkinson, Rowland. 2007. “Ecology of Sound: The Sonic Order of Urban Spaces,” Urban Studies, Vol. 44, No. 10: 1905. DOI: 10.1080/00420980701471901.

LaBelle, Brandon. 2010. Acoustic Territories: Sound Culture and Everyday Life. New York: Continuum.

Tausig, Benjamin. 2011. “Creative Reception in Urban Space, or the Art of Listening,” Journal of Urban Culture Research, Vol 2.

Post by Wendy Hsu, Steven Kemper, and Jessica Blickley.

Our series on MIT Colab Radio

We got invited to contribute to a blog post series on MIT’s Colab Radio, “a city and regional planning publication where people who are doing the daily work of improving communities can share their stories, document their projects, and express their ideas.”

This is a super exciting opportunity for us. None of us are urban planners but we want our research and engagement to be meaningful and useful for individuals whose work shapes our city. We thought there is no better home than Colab Radio to present some of our findings in progress. Our blog posts add to our community engagement efforts of sparking a dialog with urban designers, planners, and organizers about how we can learn from urban sounds.

3-part blog series on MIT Colab Radio:

Let us know if you have any thoughts!