Senior Digital Signal Processing Engineer (Audio)

Department: Software Engineering

Location: Austin

Compensation: $150K – $250K • 0.1% – 0.5%

Employment Type: FullTime

Location: Onsite — Austin, TX

Employment Type: Direct Hire, Full-Time

Job Title: Senior Digital Signal Processing Engineer (Audio)

About 9 Mothers

The modern battlefield has changed. Cheap, autonomous suicide drones have turned the tactical advantage upside down, and the world is looking for a solution. At 9 Mothers, we aren’t just "innovating"—we are building the shield.

Backed by top-tier investors, we develop AI powered machines designed to intercept and neutralize Group 1/sUAS threats in real-time. Our flagship product is a low-power, counter-drone system built for the edge—on vehicles, at bases, or in a soldier's pack.

Why 9 Mothers?

While others build for "awareness" or "long-term research," we build for the immediate survival of those in harm’s way. We are a team of hackers, engineers, and mission-driven builders who value field-ready capability over polished slide decks. If you want to see your code or hardware in the field next month—not next year—this is your playground.

Position Summary

We are seeking a Senior Digital Signal Processing Engineer to own the stack that turns raw multichannel audio into reliable bearings and alerts. You will design algorithms to function in messy outdoor conditions, optimized for low-latency execution on edge hardware to ensure our systems react faster than the threat.

Essential Duties

• Build the DSP Pipeline: Design and implement the full pipeline, including framing/STFT, filtering, coherence features, and noise/wind handling.

• Implement Beamforming & DoA: Compare and deploy approaches like MUSIC, ESPRIT, and MVDR, selecting the best strategy based on real-world field metrics.

• Hardware Partnership: Translate physical constraints (mic spacing, SNR limits) into algorithm decisions to ensure hardware and software are perfectly synced.

• Create Evaluation Infrastructure: Curate datasets and build replay harnesses and error taxonomies to answer "why did it fail" with data-driven certainty.

• Edge Optimization: Optimize for compute limits on CPU/GPU with deterministic behavior and robust fallbacks for high-stakes environments.

Requirements

• Experience: Demonstrated success delivering real-world multichannel audio, radar, or sonar systems validated on messy, imperfect data.

• Technical Depth: Strong beamforming/DoA fundamentals and sensitivity to calibration errors (phase errors, channel mismatch).

• Coding: Proficiency in Python and C++/Rust with the ability to productize, profile, and optimize code.

• Iteration: A mindset that iterates from measurements: logging → hypothesis → change → field verification.

• Compliance: U.S. Citizenship and the ability to pass a background check

Nice-to-Have

• Embedded deployment experience (NVIDIA Jetson)

• Acoustic tracking, temporal smoothing, or multi-source handling

• Prior defense startup experience

Benefits

• Meaningful Early Equity: You aren't just an employee; you are a foundational owner. Your contributions directly drive the value of your stake in the company.

• Direct Roadmap Influence: Forget the bureaucracy of big defense. You will have a seat at the table, directly shaping our product and technology trajectory from day one.

• Mission-Critical Work: We don't build for "what if." We build systems the Department of War actively needs to counter immediate, real-world threats.

• The Builder's Playground: Work in a brand-new lab fully optimized for rapid prototyping, equipped with NVIDIA Jetsons, high-end scopes, and 3-D printers.

• 100% Employer-Paid Premiums: We cover 100% of your medical, dental, and vision insurance premiums and cover 50% of healthcare premiums for your dependents.

• Unlimited PTO: We value results, not clock-watching. Take the time you need to stay sharp and recharge.

• Zero Red Tape: You report to the founders. You have the autonomy to make technical decisions that would take months of committee approval at a larger firm.

• Austin-Based Culture: Join an onsite team in Austin, TX, where we prioritize high-bandwidth collaboration and rapid field-testing.

• Relocation Assistance: We want the best talent in the room. If you aren't in Austin yet, we’ll help you get here, to make your transition to the Silicon Hills seamless.

About the Interview

1. Application screen phone call (30 min)

2. Virtual interview with co-founder/CTO + Director of Engineering (45 min via MS Teams)

3. Paid take-home consulting agreement ($500, ~4-8 hours)

4. Review work

5. Virtual interview with co-founder/CEO (45 min via MS Teams)

6. In-person visit to Austin

7. Offer